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Neuropsychology Review, Vol. 9, No. 3,1999

A Neuropsychological Approach to Intelligence

Alfredo Ardila1,2

This paper proposes that current psychometric intelligence tests are limited in evaluating cognitiveactivity. From a neuropsychological perspective, they fail to measure some fundamental cognitiveabilities such as executive functions, memory, and visuospatial abilities. The analysis of the WechslerIntelligence Scale presented shows that the original rationale for selecting the specific subtests in-cluded in the WAIS was unclear. The concept of a g factor in cognition is also analyzed, with theconclusion that the g factor continues to be controversial. The value of intelligence tests in predictingschool performance is also criticized. It is proposed that the psychometric concept of general intelli-gence should be deleted from cognitive and neurological sciences. Finally, it is proposed that, in thefuture, neuropsychological instruments sensitive to more specific cognitive abilities replace currentpsychometric intelligence tests.

INTRODUCTION

Curiously, intelligence tests do not appraise intelligence.(Anonymous)

The idea that is presented in this paper is very simple: Froma neuropsychological perspective, current psychometricintelligence tests (e.g., Wechsler Adult Intelligence Scale;WAIS) are limited in evaluating cognitive abilities. Fur-thermore, when using compound scores (e.g., IQ), it is notsufficiently apparent what these general scores measure.It is suggested that in the future, current testing methodsbe replaced by neuropsychological cognitive assessmentinstruments.

This idea, developed throughout the paper, emergesfrom the following points. (1) There are two differentsets of instruments directed to the appraisal of cognitiveabilities: psychometric intelligence tests (e.g., the WAISin its different versions) and neuropsychological assess-ment tests (e.g., Luria-Nebraska Neuropsychological Bat-tery, NEUROPSI). No evident reason seems to exist tomaintain this duality. It may be argued that psychomet-ric intelligence tests are directed to normal populations,whereas neuropsychological instruments are directed to

1 Instituto Colombiano de Neuropsicologia, Bogota, Colombia.2 Correspondence regarding this article should be addressed to the author

at 12230 NW 8 Street, Miami, Florida 33182.

brain-damaged populations. Neither argument is accurate.Psychometric intelligence tests are frequently included inthe neuropsychological evaluations of brain-damaged in-dividuals. Even a Wechsler Intelligence Scale adapted forneuropsychological purposes has been developed (WAIS-R-NI; Kaplan et al., 1991). Neuropsychological instru-ments can be and are frequently used with normal popula-tions. Initially, neuropsychological tests are administeredto normal subject populations (norming studies) beforebeing used with abnormal subject populations. It couldbe further argued that neuropsychological tests are fre-quently easy and often have a low ceiling. Indeed, neu-ropsychological tests target pathological people and, inneurologically normal people, the ceiling frequently israpidly reached. The ceiling effect varies depending on thespecific test. However, this is not an intrinsic limitation,and the ceiling can be raised. (2) From a neuropsycholog-ical point of view, intelligence tests do not evaluate someabilities that should be included as "fundamental cogni-tive abilities" (i.e., "intelligence"). An analysis of execu-tive functions (i.e., "frontal lobe" abilities), memory, andvisuospatial abilities is presented in this paper. It is em-phasized that according to contemporary neuropsychol-ogy, these abilities represent some of the most importantcognitive abilities. They are inappropriately tested usingcurrent psychometric instruments. (3) There was not suf-ficient scientific rationale for selecting the set of subtests

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1040-7308/99/0900-01 17$16.00/0 C 1999 Plenum Publishing Corporation

KEY WORDS: Intelligence; IQ; neuropsychological assessment; cognitive abilities.

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included in current intelligence batteries. Most of our cur-rent knowledge about the brain organization of cognitionhas been obtained during the past 50 years. The specificWAIS subtests currently in use were selected prior to ac-quiring this knowledge—nearly three quarters of a cen-tury ago.

The analysis of intelligence testing presented in thispaper will center on the Wechsler Intelligence Scales(WIS). There are several reasons for this. First, it repre-sents the most widely used intelligence scale, not onlyin the United States but also in many other countries.Second, it is the best studied and analyzed intelligencescale. Many research studies using the WIS in differentareas are easily available. Third, there are different ver-sions of the test (WAIS-R, WISC-III, WAIS-III, etc.) thathave attempted to overcome the shortcomings that existedin previous versions. As a result, they can be considered thebest designed intelligence scales to date; at the least, verysignificant amounts of time and effort have been devotedto their design, redesign, and use. And fourth, they are themost frequently used intelligence test battery componentsin neuropsychology. Researchers have even adapted theWAIS to the neuropsychological perspective (WAIS-R-NI; Kaplan etal., 1991).

It has to be emphasized that not all the concernspresented with regard to the WIS are applicable to otherintelligence test batteries. For example, the second mostpopular intelligence scale, the Stanford-Binet IntelligenceScale (Thorndike et al., 1986) uses a somewhat differ-ent approach to intelligence. Stanford-Binet postulates athree-level hierarchical model of intelligence. The firstlevel is represented by a general intelligence factor (g).There are three second level factors (Crystallized Abilities,Fluid-Analytic Abilities, and Short-Term Memory). Crys-tallized Abilities include Verbal Reasoning and Quanti-tative Reasoning. The third level refers to the subtestsincluded in this intelligence scale: Vocabulary, Compre-hension, Absurdities, and Verbal Relations to evaluate Ver-bal Reasoning; Quantitative, Number Series, and EquationBuilding to assess Quantitative Reasoning; Pattern Anal-ysis, Copying, Matrices, and Paper Folding and Cuttingto appraise Fluid-Analytic Abilities (Abstract-Visual Rea-soning); and finally Bead Memory, Memory for Sentences,Memory for Digits, and Memory for Objects to evaluateShort-Term Memory. It is evident that the Stanford-Binetovertly recognizes that reasoning and memory representfundamental elements of cognition.

The concept of intelligence can be criticized fromtwo different points of view. (1) Cognitive abilities mea-sured by intelligence psychological tests represent, at leastin their contents, culturally learned abilities. Performanceis influenced by a vast array of moderating variables,

including culture, ecological demands, primary language,and educational level. Test scores are associated, there-fore, not only with the subject's learning opportunities, butalso with those variables that a culture dictates worthy ofcognitive amplification (Ardila, 1995a). Different culturalenvironmental contexts will result in the development ofdifferent patterns of abilities (Berry, 1971,1979). Further,when tests are used with members of a different culture,testees often do not share the presumptions about val-ues, knowledge, and communication implicitly assumedby the test (Greenfield, 1997). (2) The specific tasks usedto tap intelligence are inappropriate. The first point hasbeen extensively analyzed, particularly in anthropology(e.g., Irvine and Berry, 1988) and cross-cultural psychol-ogy (e.g., Berry et al., 1992). In this paper, the majoremphasis will be placed on the second point (i.e., thatthe specific tasks used to tap intelligence are inappro-priate).

A general conclusion of this paper is that the con-cept of general intelligence should be abandoned. Butabandoning the concept of intelligence may seem too ex-treme. Intelligence has become a fundamental cornerstoneof contemporary psychology. Of course, there are two dif-ferent issues in this regard: the word intelligence and theexistence of a general factor (g) in cognition.

It is proposed that the word intelligence be replacedwith either cognitive abilities or simply cognition. What isthe difference? The answer is simple: intelligence is con-fusing and difficult to operationalize. Furthermore, it hasbeen frequently equated with psychometric intelligencetests (IQ).

It is also pointed out that the existence of a g fac-tor in cognitive testing is questionable. An examinationof the history of the g factor in intelligence, and the dif-ferent factor-analytic studies carried out during the lastdecades, leads to the conclusion that the assumption of ag factor is difficult to sustain. Many researchers considerthat g-based factor hierarchy confusing and misleading(e.g., Ceci, 1990; Lezak, 1995).

Finally, it has to be emphasized that intelligence isobviously a construct, not a physical entity. Frequently,however, the term intelligence has been used as if it werea physical entity, a reification that can be easily and objec-tively measured. In this paper, it is argued that the constructof intelligence is no longer tenable, and thus, measures ofgeneral intelligence are inappropriate and misleading.

Many words from popular language have been in-corporated into psychology. Terms such as will, mind, andconsciousness are just a few examples that have been elim-inated with the evolution of psychology because their pre-cise meaning is vague. For the same reason, it is proposedthat the term intelligence should also be removed.

Intelligence and Neuropsychology 119

INTELLIGENCE TESTING: A BRIEFHISTORICAL OVERVIEW

The attempt to measure intelligence represents oneof the major endeavors in 20th century psychology. Atremendous amount of research has been directed to un-derstanding the organization of intellectual activity anddiscussing the procedures appropriate to its measurement.

In 1904 the Ministry of Education in Prance com-missioned Alfred Binet and Theophile Simon to developa practical procedure to distinguish between mentally re-tarded and normal children at school. To fulfill this pur-pose, they developed a kind of developmental scale de-scribing the types of abilities that were normally expectedat different ages (Binet, 1905,1908). The concept of "men-tal age" was introduced to refer to the level of developmentexpected at each age. Later, Stern (1912) introduced theconcept of IQ. The Binet-Simon tests were rapidly adoptedin England, the United States, and other countries. In theUnited States, Terman (1916), at the University of Stand-ford, adapted and standardized the scales presented byBinet and named them the Stanford Revision of the BinetScale, or simply Stanford-Binet. Terman also further de-veloped the concept of IQ. Nonetheless, how to understandcognitive abilities measured in intellectual tests remainedsignificantly controversial.

Two different interpretations of cognitive abilitiesrapidly became evident: (1) There is a general intelligencefactor that potentially may be measured and even quanti-fied; and (2) there are different cognitive abilities, not asingle one. That is, single compound scores are not ac-ceptable.

The "g" Intelligence Factor

Spearman (1904,1923) may be considered the mostimportant representative of the first point of view. He hy-pothesized a two-factor theory of intelligence. He sup-posed that any test measures a g factor common to allother cognitive tests; and a specific factor (s) unique tothat particular test. The relation between g and s compo-nents may be variable, but g is always included in anycognitive tests. Tests without the g factor may be tests ofsensory or motor abilities, but they do not represent cog-nitive tests. The existence of this g factor constitutes thetheoretical basis to accept that intelligence can be quanti-tatively measured using a simple score (IQ). Spearman'stheory was subjected to diverse fundamental criticism onempirical grounds. However, "while Spearman was awarethat his theory had been empirically refuted, he continued

to emphasize the importance of a common factor in intel-ligence" (Brody, 1992, p. 13).

Multiple-Factor Approaches

The most distinguished representant of the secondpoint of view was L. L. Thurnstone (1938, 1947), whofurther developed factor analysis, attempting to obtain themost parsimonious solutions of the data to which they wereapplied. He introduced new concepts and more sophisti-cated procedures in factor analysis, such as oblique-factorstructure and centroid methods. He proposed a relativelylimited number of factors that would correspond to the fun-damental or primary mental abilities: Space, Verbal Com-prehension, Word Fluency, Induction, Perceptual Speed,Deduction, Rote Learning, and Reasoning. He supposedthat each factor should correspond to certain specific ner-vous system activity. Further studies (e.g., Kaiser, 1960)have significantly supported most of the original primaryfactors proposed by Thurstone.

Vernon (1950) developed a kind of hierarchical modelto describe the organization of cognitive abilities. He as-sumed two major or second-order factors to group primaryabilities or primary factors: Verbal-Educational (v:ed) andSpatial-Mechanical (k:m) abilities. Thus, there was a kindof hierarchy in intelligence from the most general factorg, to the major factors v:ed and k:m, to the minor factorsor primary abilities, and finally to those factors specific toeach test.

Guilford (1967,1968; Guilford and Hoepfner, 1971)took a somewhat different approach. He proposed athree-dimensional classification of intelligence includingcontents (letters, numbers, words, and behavioral descrip-tions); operations (memory, evaluation, convergent think-ing, and divergent thinking); and products (units, classes,relations, systems, transformations, and implications).Consequently, according to Guildford, 120 different in-tellectual abilities could be distinguished. He supposedthat empirical data would support the existence of thishigh number of intellectual abilities.

Cattell (1971) proposed that more than one second-order analysis factor could be found. He distinguished be-tween "Fluid Intelligence" (corresponding to and reflect-ing a pattern of neurophysiological and incidental learninginfluences) and "Crystalized Intelligence" (highly sensi-tive to each person's unique cultural, educational, and en-vironmental experiences). This distinction rapidly becamequite popular. Cattell's distinction between two differenttypes of intelligence is similar to the two major intellec-tual factors proposed by Hebb (1942): Intelligence A and

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Intelligence B. Intelligence A represents the basic biolog-ical ability to acquire knowledge. Intelligence B reflectsthe influence or expression of acculturation, education,and personal experiences.

The Idea of Multiple Intelligences

Gardner's multiple intelligence approach might beinterpreted as a return to Thurnstone. Gardner (1983) pro-posed the existence of different and independent types ofintelligence. In developing his model of intelligence, hebegan with several observations: (1) Damage in differ-ent neural structures may result in impairing certain abil-ities while sparing other abilities; that is, isolated defectsin some types of cognition can be observed in cases ofbrain pathology (a procedure known in neuropsychologyas "double dissociation"). (2) Individuals such as idiot-savants demonstrate a significant dissociation in differentcognitive abilities. That is, in non-brain-damaged indi-viduals intellectual abilities may be dissociated, and evenextremely dissociated. (3) Every type of ability is iden-tified by a specific set of operations related to a neuralmechanism; in this regard, Gardner is attempting to rec-oncile the idea of several types of intelligence with currentresearch about brain organization of cognition. (4) A spe-cific developmental history for each type of intelligence;that is, different cognitive abilities ("intelligences") de-velop independently in a child. (5) An evolutionary his-tory exists for each intelligence; that is, different intelli-gences may have different origins in subhuman speciesand may have evolved in different ways. (6) Experimen-tal psychology supports the existence of different intel-ligences. (7) Psychometric studies support the indepen-dence of different cognitive abilities; Gardner insists thatpsychometric research has not investigated widely enoughthe diversity of intellectual abilities that are observed inreal contexts. (8) Susceptibility of different abilities to en-coding in a symbolic system; he proposed that cognitiveabilities tend to be encoded in culturally different devisedsymbolic systems.

Departing from these considerations, Gardner pro-poses six different types of intelligence: Linguistic, mu-sical, logic-mathematical, spatial, body-kinesthetic, andpersonal. This group of intelligences may partially corre-spond to Thurnstone's primary mental abilities. However,Gardner is relying not simply on psychometric proceduresbut also on a broad array of contemporary research, includ-ing contemporary neuropsychology.

In brief, Gardner proposes a relatively limited num-ber of basic and independent abilities or types of intelli-gence. The similarity with Thurnstone's primary mental

abilities, and contemporary factor analytic studies of neu-ropsychological tests, is remarkable.

Sternberg's Triarchic Theory

Sternberg (1988) defined intelligence as "the men-tal activity underlying purposive adaptation to, shapingof, and selection of real-world environments relevant toone's life" (p. 69). The triarchic theory of intelligence con-sists of three closely interrelated subtheories: a contextualsubtheory, a componential subtheory, and an experientialsubtheory (Sternberg, 1985).

The contextual subtheory limits intelligence to men-tal activity underlying environments relevant to one's life.In consequence, intelligence should be conceptualizedconsidering the real conditions existing in the immediateenvironment. Intelligence represents adaptation to one'senvironment. Mental activity is directly inferable throughtechniques widely available to cognitive psychology.

The componential subtheory states that the mentalmechanisms are those that affect and are affected by con-text. Intelligence makes sense only within a particular con-text. The basic "mental unit" of analysis in this subtheoryis the information processing component. This refers to theprocess transforming sensory inputs into conceptual repre-sentations, transforming a conceptual representations intoanother, or transforming conceptual representations intomotor acts.

The experiential subtheory states that tasks are par-ticularly relevant to the measurement of intelligence whenthey measure cognitive performance either when a task orsituation is novel or when the task is in the process ofbecoming automatized.

Sternberg (1997) has attempted to apply his interpre-tation of intelligence to testing in the field of intelligenceand the understanding of lifelong learning. His interpre-tation of intelligence allows significant cultural variationsand emphasizes the understanding of the behavioral con-text.

A Processing Speed Interpretation of Intelligence

It has also been proposed that intelligence dependson what may be called "the neural efficiency of the brain"(Eysenck, 1986). Several recent studies have demonstratedthat the time required to perform some simple perceptualtests are significantly correlated with psychometric intel-ligence test scores. This means that intelligence may berelated to some characteristics of information processingin the central nervous system. Jensen (1987) observed a


correlation between choice reaction time and scores onintelligence tests. These correlations, however, were notparticularly impressive (about —0.20 to —0.30). It wasobserved that reaction time was inversely correlated withIQ and measures thought to singly predict approximately10-15% of the variance in IQ (Brody, 1992). Higher cor-relations on the order of -0.40 using more complex reac-tion time techniques have been reported by Frearson andEysenck (1986).

Nettlebeck (1987) found a correlation on the orderof —0.50 between inspection time and IQ. The techniqueused consisted of tachistoscopic presentations of two ad-jacent vertical lines followed by a masking stimulus. Thetime of exposure varied and a psychophysical function wasobtained. The task was used to ascertain the minimal ex-posure time required to obtain a certain level of accuracyin recognizing which one of the two lines was longer.

Reed and Jensen (1992) have used visual evoked-potentials to assess what they call nerve conduction ve-locity. They calculate this velocity by dividing the sub-ject's head length by the latency of an early visual evokedpotential component. Using this procedure, they report acorrelation between nerve conduction velocity and intel-ligence on the order of 0.20 to 0.30.

In brief, some significant correlations have been es-tablished between speed in information processing andscores on psychometric intelligence tests. These measures,however, usually predict only a relatively modest percent-age of the variance.

Neuropsychologically Oriented Intelligence Tests

Some attempts have been made to approach the con-cept of intelligence and to develop intelligence test bat-teries based on a neuropsychological perspective. Two ofthese attempts will be briefly examined: The KaufmanAdolescent and Adult Intelligence Test (KAIT; Kaufmanand Kaufman, 1993,1997) and the Cognitive AssessmentSystem (CAS; Das etal., 1994; Naglieri and Das, 1996).

The KAIT provides three types of scores: Fluid, Crys-talized, and Composite IQS. It is applicable to people be-tween the ages of 11 and 85. According to the authors,the tests were developed based on the models of Piaget'sformal operations and Luria's planning ability in an at-tempt to include high-level decision making tasks (Luria'sthird functional unit). The Crystalized Scale includes Def-inition, Auditory Comprehension, Double Meaning, andFamous Faces subtests. The Fluid Scale includes RebusLearning, Logical Steps, Mystery Cards, and Memory forBlock Designs. The KAIT also include two additional sub-tests (Rebus Delayed Recall and Auditory Delayed Recall)

and a supplement test (Mental Status). Each IQ (Fluid,Crystalized, and Composite) has a mean of 100 and stan-dard deviation of 15.

Naglieri and Das (1996) suggested that intelligenceshould be seen as a cognitive construct, integrating neuro-physiological findings, cognitive processing research, andsociocultural components of human performance. Theybase their intelligence theory on Luria's interpretationabout the three brain functional units (motivation-emotion, processing-storing information, and planning-controlling behavior). They assume that intelligence con-sists of these three components: attentional processes thatprovide focused cognitive activity, information processesof two types (simultaneous and successive), and planningprocesses that provide control of attention; the use ofinformation processes, internal and external knowledge,and cognitive tools; and self-regulation to achieve de-sired goals (Naglieri, 1997). They refer to their theory asthe Planning, Attention, Successive, Simultaneous (PASS)theory of intelligence (Das et al., 1994). They then devel-oped a Cognitive Assessment System (CAS) applicable tochildren up to the age of 18. The CAS includes measuresof attention (Expressive Attention, Number Detection, Re-ceptive Attention), simultaneous processing (Matrices,Figure Memory, Verbal-Spatial Relations), successive pro-cessing (Word Series, Sentence Repetition, SentenceQuestion, Speech Rate), and planning (Number Match-ing, Planned Codes, Planned Connection).

Both test batteries have at least three major commonpoints: (1) They relate intelligence with brain activity andin this regard represent neuropsychologically oriented in-telligence scales; (2) they are based on Luria's theoryabout brain organization of cognition; and (3) they attemptto include those cognitive abilities associated with pre-frontal functions (Luria's third functional unit; prefrontalor "executive" functions). In this regard, they recognizethat executive functions must be regarded as crucial ele-ments of intelligent behavior.

THE WECHSLER INTELLIGENCE SCALES

What is intelligence? Many definitions of intelligencehave been proposed (e.g., Binet, 1908; Jensen, 1980;Sternberg, 1985; Wechsler, 1944). In current literature,we still find a wide variety of definitions, many of whichmake reference to the mental abilities. For the purposeof this analysis of intelligence tests, Wechsler's definitionwill be used. Wechsler (1944) defined intelligence as "theaggregate or global capacity of the individual to act pur-posefully, to think rationally and to deal effectively withhis environment" (p. 3).

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This definition can be divided into four different ele-ments: (1) Intelligence is an aggregate or global capacity,(2) to act purposefully, (3) to think rationally, and (4) todeal effectively with the environment.

The first element of Wechsler's definition of intel-ligence refers to a core issue: Is there such a thing as aglobal or general intelligence, or rather, is intelligence anaggregate of abilities? In his defintion, Wechsler does nottake a definite position, but he assumes a theory of generalintelligence in developing his test battery (Full Scale IQ).Yet he recognizes at least two major types of intelligence:verbal and performance intelligence. This question aboutone or several intelligences continues up to the presentday (see Neisser et al., 1996).

The second element in Wechsler's definition of in-telligence ("to act purposefully") could be understood asthe control, organization, and planning of behavior. Actingpurposefully is evidently a frontal lobe function (executivefunction) if taken from a neuropsychological perspective(e.g., Luria, 1980; Stuss and Benson, 1986).

The third element ("to think rationally") might beunderstood as either organization of cognition (metacog-nition) or problem-solving ability. In either case, the def-inition deals with executive functions (Stuss and Benson,1986). It means that intelligence, to a significant degree,refers to executive functions. From the neuropsychologi-cal perspective, this approach may sound quite attractive(i.e., intelligence means planning behavior and organiz-ing cognition). Unfortunately, it will be explained thatWIS blatantly fails to evaluate executive functions. Thereis an overt discrepancy between the defintion of intelli-gence presented by Wechsler and the testing included inthe WIS.

The final element ("to deal effectively with the envi-ronment") refers to the functional criteria of intelligence.Of course, intelligence may be understood not only froma psychometric perspective but also from a functional per-spective (Pirozzolo, 1985). Wechsler appropriately recog-nizes that intelligence has to be considered with regardto the specific environment. The physical and social en-vironment can be quite different between Seattle and theAmazonian jungle, as well as between different subcul-tures existing in a complex city such as New York. Colom-bian street children can deal extremely well with their cityenvironment, even though from a psychometric point ofview they may score at the level of mental retardation.Unfortunately, it is not so easy to evaluate effectiveness indealing with the environment from the outside. This canonly be appropriately evaluated from inside the culture orsubculture itself. In this regard, intelligence becomes ananthropological issue.

The question at this point is how Wechsler decidedthat the WIS subtests he selected were the most appropriate

to evaluate the capacity of the individual to act purpose-fully, to think rationally, and to deal effectively with hisenvironment. Wechsler (1944) explains that:

In arriving at our final choice of tests we used the followingprocedure: (1) Careful analysis was made of the various stan-dardized tests of intelligence now in use. These were studieswith special attention to the author's comments with referenceto the type of functions measured, the character of the popula-tion on which the scales were originally standardized, and theevidence of the test's reliability. (2) An attempt was made toevaluate each test's claim to validity as evidenced by its degreeof correlation (a) with other recognized test and, (b) more im-portantly still, with subjective ratings of intelligence. The laterincluded teachers' estimates, rating by army officers (as in thecase of the Army Alpha and Beta), and estimates of businessexecutives (as in the case of various tests which had been triedout in industry). (3) An attempt was made to rate the tests onthe basis both of our own clinical experience and of that ofothers. (4) Some two years were devoted to the preliminaryexperimental work of trying out various likely tests to on theseveral groups of known intelligence level, (p. 76)

Unfortunately, Wechsler fails to explain exactly howthese steps were taken.

DO INTELLIGENCE TESTS PREDICTSCHOOL PERFORMANCE?

The most frequent argument of the defenders of in-telligence testing and IQ is that intelligence tests can ina reliable way predict school performance (e.g., Jensen,1980). As a matter of fact, this was the initial purpose ofintelligence tests.

The influence of educational variables on intelligencetest performance represents a well established observation(e.g., Anastasi, 1988; Cronbach, 1990). Educational at-tainment significantly correlates with scores on standardtests of intelligence. This correlation ranges from about0.57 to 0.75 (Matarazzo, 1972). Correlations with verbalintelligence subtests are usually higher (from about 0.66to 0.75) than correlations with performance intelligencesubtests (from about 0.57 to 0.61). But correlation doesnot mean causality; it simply means association.

The crucial question is: Do intelligence tests reallypredict school performance? Or, do schools train thoseabilities appraised in intelligence tests? To answer thesequestions is not easy, even though frequently the interpre-tation has been that IQ does predict school performance(e.g., Hunter, 1986). Other researchers, however, considerthat IQ scores are, to a significant extent, a measure ofdirect and indirect school learning (e.g., Ceci, 1990).

Ceci (1991) presented an extensive and detailed re-view of available data in this area. The general conclusionis that school attendance accounts not only for a substantial


portion of variance in children's IQ but also apparentlysome, though not all, of the cognitive processes that un-derpin successful performance in IQ tests. The magni-tude of this influence ranges between 0.25 to 6 IQ pointsper year of school. As a result, the association betweenIQ and education cannot be interpreted as indicating thatIQ predicts school success. Intelligence and schoolinghave complex bidirectional relationships, with each oneinfluencing variations in the other (Ceci and Williams,1997).

There are two additional observations that should beemphasized. (1) The largest correlations between IQ andschool performance are not found with Full Scale IQ butwith Verbal IQ, and particularly with some verbal subtests(e.g., Vocabulary). So, the question that might be raised is,Why bother to administer the complete intelligence scaleif the verbal subscale (and even one single subtest) is suf-ficient, and may even be better? And, (2) IQ may "predict"performance in language, reading, writing, and arithmeticbut cannot predict performance in other areas, such asdrawing or music. Simply speaking, if language tests areused as predictors, verbal performance can be predicted.That is quite obvious. Evidently, our current educationalsystem is significantly biased in favor of verbal abilities.This is not true in other cultures' educational systems, noris it always true in all of our educational programs. It there-fore seems questionable that the WIS is a good predictorof school performance in music and art schools.

Ceci (1991) emphasizes that there is a circularity inthe association between school performance and IQ. IQtest items were initially selected from those items that ac-cording to teachers' opinions, poor learners had the mostdifficulty answering in class. Variants of these questionsare still found in large number on contemporary IQ tests.So, it is obvious that IQ tests would predict school suc-cess, as they were composed of items that poor learnersfound most difficult. Consequently, school failure is bothexplained as a lack of intelligence and is itself the basisfor the definition of lack of intelligence. The circularity isevident.

From a neuropsychological perspective, this represents anextremely important observation when constructing anytheory about the organization of cognitive abilities; inde-pendent cognitive abilities can be independently impairedand can independently deteriorate during normal and ab-normal aging. According to Lezak (1995), the concept ofintelligence has limited application. The concept of IQ,she notes, represents so many kinds of more or less con-founded functions as to be conceptually meaningless. Sheconcludes that the "IQ as a score is inherently meaning-less and not infrequently misleading— IQ as a catchwordhas outlived whatever usefulness it may once have had andshould be discharged" (p. 25).

Heterogeneity of cognitive abilities is supported byempirical neuropsychological data. This is true not onlyin abnormal but also normal populations. As an illustra-tion, Ardila et al. (1998) selected a homogenous sample ofnormal subjects (300-subject sample, aged 17-25 years;all of them right-handed, middle-class male universitystudents). An extensive neuropsychological test batterywas administered including language, memory, perceptualabilities, concept formation, and praxis abilities. Forty-one different scores were calculated. Table I presents thedispersion in scores observed on some of the most "classi-cal" psychological and neuropsychological tests (WAIS,Wechsler Memory Scale, etc.) that were included in thisresearch. It is evident that a particularly high dispersionin scores is found in this completely normal and homoge-nous population. The ratio between the lowest and highestscores in most tests was around 1:5-l 0. In some test scoresit was even higher. In the WAIS subtests, dispersion wasparticularly high in Information, Arithmetic, Block de-sign, Object assembly, and Digit-symbol. It was relativelylower in Digits, Picture completion, and Picture arrange-ment. Even in young, normal, and highly educated indi-viduals there is a very significant dispersion in the per-formance of usual psychological and neuropsychologicaltest scores. Significant intersubject and intrasubject dif-ferences have to be taken into consideration in any theoryabout organization of cognition, and in the evaluation ofintellectual abilities.

A NEUROPSYCHOLOGICAL PERSPECTIVE OFCOGNITIVE ABILITIES AND THEIR MEASURE

In neuropsychology a significant opposition to theuse of compound IQ scores is frequently observed. Lezak(1995), for example, stressed that neuropsychological ob-servations demonstrate that there are independent intel-lectual functions; Brain damage can impair certain func-tions while sparing others. In consequence, compound,global, or total scores can be artificial and meaningless.

Luna's Interpretation of Brain Organizationof Cognition

No doubt, one of the most influential theoreticiansin contemporary neuropsychology has been A. R. Luria.Luria (1980) proposed that cognitive abilities represent"functional systems." The concept of the functional sys-tem is understood as a group of interconnected biologicaloperations that produces a particular biological effect. The

functional system is based on a complex dynamic constel-lation of stages, situated at different levels of the nervoussystem, which in performing an adaptative task, may bechanged without the task itself being changed. To write,for instance, represents a complex psychological process(functional system) that requires the participation of mul-tiple areas of the brain; each of these areas makes its par-ticular contribution to the whole system. A focal lesion ofthe brain will disrupt the ability to write at a particular level(the ability to perform the skilled movements required forwriting, the spatial organization of writing, the selectionof words, the ability to sequence graphemes, etc.). How-ever, such particular focal damage will also disrupt all thefunctional systems for which that particular operation isrequired. For instance, the patient will not only have dif-ficulties for the spatial organization of writing but also

for the spatial organization of numbers, figures, drawings,etc. In all the functional systems in which the paricularability is included, the defect will be apparent. The braindamage produces not the loss of a specific cognitive pro-cess (functional system), but its disturbance at a specificlevel. This implies that neuropsychological assessmentwill be aimed at disclosing the fundamental defects un-derlying the apparent deficits. For this purpose, it will benecessary to administer to the patients different types oftasks and to analyze how the particular difficulties in per-forming each one of them are manifested.

Clinical-anatomical correlations were widely devel-oped by Luria. As a matter of fact, he is a precursor of themethod of the superimposition of lesions to disclose criti-cal areas in a particular type of disorder. His study of 800patients to determine the critical brain area for phonemicdiscrimination deficits has become classic. This procedureof superimposing lesions to highlight critical areas re-sponsible for clinical syndromes is extensively used in thepresent-day neuropsychological research (e.g., Damasioand Damasio, 1989; Kertesz, 1983). Luria strived to es-tablish correlations between brain pathology and distur-bances at specific levels of information processing (e.g.,phonemic discrimination), not to correlate brain pathologywith performance in specific tests. Tests may be changed,but since some specific level of information processingwould still be required, impairment will be manifested.Because performance on even apparently very simple testscan require the participation of different brain systems,performance on such simple tests can be altered as a con-sequence of very different brain pathology, although thespecific errors will be different. Many different types ofbrain pathology can alter, for instance, calculation abili-ties; however, in each case the difficulty (and the errors)will be the result of a disturbance at a different level. Pa-tients with frontal lobe damage and patients with angulargyros damage can both present with serious difficultiesin performing simple calculation tests. However, the un-derlying impaired mechanism and the type of errors mani-fested are quite different (Rosselli and Ardila, 1989). Con-sequently, the validity derived from correlating the site ofthe brain pathology with performance on a particular testappears, in Luria's interpretation, as a very crude approx-imation.

For Luria, the information collected from the obser-vation of brain-damaged patients should be helpful fordeveloping a more accurate picture of brain organizationof cognitive processes. If we knew well enough how thebrain works we should be able to accurately predict brainpathology when analyzing in detail the performance of apatient on a set of tests. The departure point in the neu-ropsychological assessment is the knowledge about how

Ardila124

Table I. Performance of 300 Normal Subjects in "Classical"Psychological and Neuropsychological Tests

Test

WAISInformationSimilaritiesArithmeticVocabularyComprehensionDigitsPicture completionPicture arrangementBlock designObject assemblyDigit-symbol

WMSInformationOrientationMental ControlLogical MemoryVisual ReproductionAssociative Learning

Verbal FluencyPhonologicSemantic

The Rey-Osterrieth Complex FigureCopy

Immediate memoryFinger Tapping Test

Right handLeft hand

Reading speed (words/minute)WCST

Categories achievedPerseverative errorsNonperseverative errors

Mean

16.718.711.853.517.611.616.825.339.331.756.0

5.84.97.3

15.112.118.1

11.614.7

34.928.2

61.253.0

172.3

5.79.69.3

SD

4.43.67.79.24.52.22.85.57.47.6

15.0

0.40.21.93.21.93.1

2.52.5

1.75.0

10.48.7

46.7

1.19.38.1

Range

4-276-263-18

18-766-275-178-21

10-360-482-44

11-90

3-64-50-95-216-193-26

3-177-25

26-369-36

23-8821-7964-426

0-60-770-62

Ratioa

:6.7:4.3:6.0:4.2:4.5:3.4

1:2.61:3.6

—1:22.01:8.2

1:2.01:1.2

—1:4.21:3.11:8.6

1:5.61:3.6

1:1.41:4.0

1:3.81:3.71:6.6

———

aRatio between the highest and lowest scores. When the lowest scoreis zero, the ratio cannot be calculated. From the mathematical point ofview, it would be infinite. These conditions are indicated by a dash.

125

language area (Broca's area), and (6) the primary motorcortex controlling language articulation. Benson pointsout that depending on the material used in reading, otheradditional brain areas could also be involved in the read-ing process. This whole array of brain areas would rep-resent the "brain system" (Ardila, 1995b) underlying thereading aloud process, and supporting the "functional sys-tem" for reading, according to a Lurian interpretation. Incase of damage in any of these written language process-ing levels, a deficit in reading will appear, even thoughit would be different depending on the specific impairedarea. Furthermore, other abilities also relying on one ofthese processing levels ("factors") would be also affected.

Contemporary neuroimaging and electrophysiologi-cal techniques have provided most valuable informationabout brain activity during performance of different cog-nitive tasks. Thus, departing from measures of focal brainmetabolism, positron emission tomography allows oneto visualize levels of brain activity and focal involve-ment during different conditions. It has been observed thatwhen performing complex intellectual tasks (e.g., readingaloud, speaking, etc.) a complex matrix of activated ar-eas is revealed (Posner et al., 1988). Different brain ar-eas participate, making specific contributions to the per-formance during, for example, a reading task: occipital(visual perception), temporal (language decoding), andfrontal Broca's area (language control and production)(Pettersen et al., 1989). For each one, a somehow lim-ited region is fully activated, where some other areas canbe only partially active (Price et al., 1994). While speak-ing, a specific activation of the left mouth area can beobserved, as well as in the superior temporal lobe and thesupplementary motor area.

Factor Analysis in Neuropsychology

In the neuropsychological domain, factor analysishas been more frequently applied to some specific tests andscales directed to measure single cognitive abilities. Forexample, several factor analytic studies of the WechslerMemory Scale are available to date (Ardila and Rosselli,1994; Bornstein and Chelune, 1988; Elwood, 1991; Roidetal., 1988; Wechsler, 1987). Nonetheless, factor analysesof extensive neuropsychological battery tests are scarce.

Ponton etal. (1994) administered a neuropsycholog-ical test battery including 10 different tests to 300 nor-mal subjects. A factor analysis was used and five differentfactors were found: a Verbal Factor (measured basicallythrough verbal fluency and naming), a Learning Factor(measured specially with an auditory verbal learning test),a factor related to the Speed in Processing Information

the brain works, not the knowledge about how to apply aseries of tests in standardized conditions.

It is interesting to note that Luria extensively, butnot systematically, used the term factor to refer to thedeficit that can underlie an overt clinical disorder. At othertimes he simply referred to the basic deficit or underlyingdefect affecting normal psychological performance. And,undoubtably, he did not use the term factor with a mathe-matical meaning (i.e., factor analysis).

At this point, the question arises as to which "fac-tors" underlay performance in different neuropsycholog-ical tests. These factors would, in consequence, representthe basic elements of cognition, Luria discussed this ques-tion in some detail with regard to language. In his lastbook Basic Problems of Neurolinguistics" (1976a), Luriaanalyzed the factors that can underlie the different apha-sic syndromes (Table II). As a matter of fact, these samefactors had been previously pointed out by Luria yearsbefore. However, it is not easy to deduce the impairedfactors in other neuropsychological syndromes (e.g., ag-nostic or apraxic disorders). This "factorial theory" of cog-nitive activity represents one of the most interesting andoutstanding points in Luna's neuropsychological perspec-tive. Unfortunately, Luria did not completely develop thisfactorial theory of psychological activity.

Further Developments

Luria's interpretation of brain organization of cogni-tive activity has received support from contemporary re-searchers in the area. Thus, for Benson (1994), any com-plex psychological activity requires the participation ofdifferent brain areas. As an example, according to Benson(1982), six different brain areas participate under normalconditions in reading aloud: (1) primary visual cortex,(2) association visual cortex, (3) angular gyrus, (4) tempo-ral areas involved in language recognition, (5) the frontal

Intelligence and Neuropsychology

Table II. Factors Underlying Different Aphasia Syndromes,According to Luria (1976a)a

Aphasia Type

Acoustic-AgnosticAcoustic-AmnesicAmnesicSemantic

Afferent MotorEfferent MotorDynamic

Impaired Factor

Phoneme discriminationVerbal memorySemantic structure of wordsUnderstanding logical-grammatical

(quasi-spatial) structuresArticuleme discriminationDisturbances in speech kinetic structureVerbal initiative

a "Factor" in Luria's theory refers to the fundamental defect responsiblefor a particular neuropsychological syndrome.

126 Ardila

(attention; measured with Digit-symbol subtest), a VisualProcessing Factor (measured with the Rey-OsterriethComplex Figure), and finally, a Psychomotor Speed Factor(measured with the Pin Test).

Ardila et al. (1994) administered a general neuro-psychological test battery to a 98-subject sample. Theirbattery included language, memory, spatial abilities, con-cept formation, and praxis abilities tests. A factor analysiswith varimax rotation found nine different factors account-ing for about 70% of the variance. Factor I (Verbal Fac-tor; accounting for 14.2% of the variance) was measuredby a Sequential Verbal Memory Test and Verbal Fluencysubtests. Factor II (accounting for 12.9% of the variance)was measured by the WMS Visual Reproduction subtests(Nonverbal Memory and Constructional Factor; imme-diate and delayed reproduction) and the Rey-OsterriethComplex Figure (copy and immediate reproduction). Fac-tor III (Verbal Memory Factor; accounting for 9.8% of thevariance) was measured by the WMS Logical Memorysubtests (immediate and delayed). Factor IV (Fine Move-ments Factor; accounting for 6.4% of the variance) wasassociated with fine movements (tapping subtests, rightand left hand). Factor V (Verbal Knowledge; accountingfor 6.0% of the variance) was mainly measured by theInformation subtest of the WMS and the Boston NamingTest. Factor VI (Praxis Ability Factor; accounting for 5.5%of the variance) represented ideomotor praxis tests. Fac-tor VII (Delay Associative Learning Factor; accountingfor 5.4% of the variance) was measured by the DelayedAssociative Learning subtest, and Factor VIII (ArithmeticFactor; accounting for 5.0% of the variance) was measuredby Digit Span. Factor IX (Mental Control Factor; account-ing for 4.4% of the variance) was measured by the MentalControl subtest of the WMS. Correlations between sometests were negative (e.g., between Logical Memory fromthe WMS and Rey-Osterrieth Complex Figure-Copy con-dition). Several correlations were around zero. This obser-vation is particularly important from the point of view ofthe existence of a general factor in cognition (g factor).

Ardila et al. (1998) administered a comprehensiveneuropsychological test battery: language, memory, per-ceptual abilities, concept formation, and praxis abilitiestests to 300 normal subjects. Forty-one different scoreswere calculated. It was found that some of the tests pre-sented a complex intercorrelation system, whereas othertests presented few or no significant correlations. A factoranalysis with varimax rotation of the neuropsychologi-cal battery tests was performed. Five different factors ac-counted for 63.6% of the total variance. Factor I (26.7%of the variance) represented a clearly Verbal factor. Fac-tor II was a perceptual or Nonverbal factor (12.5% of thevariance). Factor III (9.8% of the variance) correlated with

the different scores of the Wisconsin Card Sorting Test.Factor IV (7.9% of the variance) was a Fine Movementsfactor, and Factor V (6.7% of the variance) represented aVerbal Memory factor.

Ostrosky etal. (1999) administered a short neuropsy-chological test battery assessing a wide spectrum of cog-nitive functions including orientation, attention, memory,language, visuoperceptual abilities, and executivefunctions. Normative data in an 800-subject sample from16 to 85 years of age, and from zero to 24 years of educa-tion were obtained. A factor analysis with varimax rotationdisclosed seven different factors. Factor I (accounting for28.6% of the variance scores) best correlated with Dig-its backwards, Copy of a semicomplex figure, Calculationabilities, and Language Comprehension. Factor II (9.6%of the variance) highly correlated with the writing scores.Factor III (accounting for 6.1% of the variance) best cor-related with verbal fluency tests. Factor IV (accounting for5.7% of the variance) was correlated with motor functions.Factor V (accounting for 4.3% of the variance) correlatedwith all the recall scores. Factor VI (accounting for 3.9%of the variance) correlated with Orientation in Space. Fac-tor VII (accounting for 3.6% of the variance) correlatedwith Orientation in Person.

In summary, several factor analyses of extensive neu-ropsychological test batteries have yielded quite similarresults: Some 5-10 factors are found, accounting for abouttwo-thirds of the total variance. The first factor accountsfor some 15-30% of the total variance, and it is usually averbal factor. Some additional factors are also observed:spatial, memory, perceptual, fluency, motor skills, etc. Thedamage in the "brain systems" supporting the intellectualactivities corresponding to these factors (verbal abilities,spatial abilities, verbal fluency, etc.) would result in spe-cific neuropsychological syndromes (aphasia, spatial ag-nosia, amnesia, etc.). These factors should be matchablewith the neuropsychological syndromes found in casesof brain pathology (see Table III). Nonetheless, it doesnot seem realistic to suppose that the exact number ofthese factors can be determined. From a factor analysisperspective, the factors to be found obviously depend notonly on the types of tests that are included but also on someadditional variables (e.g., the subjects included in the anal-ysis, the type of factor analysis, etc.). From a neuropsycho-logical perspective, to exactly pinpoint the cognitive syn-dromes observed in cases of brain pathology is not an easytask, at least at the moment. As an illustration of this point,we do not know well enough how to classify spatial dis-turbances associated with brain pathology (e.g., Benton,1989; De Renzi, 1982, 1985; Hecaen, 1962; Hecaen andAlbert, 1978; Morrow and Ratcliff, 1988; Newcombe andRatcliff, 1989). We do not know yet well enough either


frequency across different factorial studies. This is ob-served in different cognitive areas: reasoning, language,memory, visual perception abilities, etc. Table IV presentsa summary of these relatively constant factors found acrossdifferent factor analytic studies. From a neuropsycholog-ical perspective, these factors are expected to be impairedin cases of focal brain pathology. Some neuropsycholog-ical syndromes are expected to be observed in cases ofdisruption of these brain systems supporting these basiccognitive factors.

Frontal Lobes and Intelligence

Long ago it was noted that frontal damage did notresult in evident deficits in psychometric intelligence tests(Hebb, 1939; Hebb and Penfield, 1940). This was trueeven in cases of bilateral frontal lobectomy. It was some-how surprising to find that IQ in patients with frontal lobedamage could be normal (Hebb, 1945). These initial obser-vations carried out during the 1940s have been further doc-umented in neuropsychology (e.g., Brazzelli etal., 1994;Damasio and Anderson, 1993). Milner (1963) reporteda mean loss of only 7.2 IQ points following dorsolateralfrontal lobectomies, with mean postoperative IQ scores re-maining in the average range. This observation meant thateither frontal lobes do not have much to do with intelli-gence or psychometric intelligence tests were not sensitiveto frontal lobe deficits ("executive dysfunctions," accord-ing to contemporary terminology).

Teuber (1972) carried out a rather extensive researchproject in order to pinpoint the deficits associated withfrontal pathology. He compared patients with right frontal,

how exactly to classify language disturbances associatedwith brain damage (e.g., Benson and Ardila, 1996). Andwe do not know well enough the exact variants of theprefrontal syndrome (Damasio and Anderson, 1993).

Interestingly, some fundamental intellectual factorscan be found throughout different psychometric factoranalytic studies. Carroll (1993) analyzed 461 factor-ana-lytic studies presented in the literature up to date. He ob-served that some factors tend to appear with a significant

Table HI. Factors Observed in Ardila etal. (1 994) Neuropsychological Test Battery, the Tests MostSaturated by These Factors, and Probable Neuropsychological Syndromes that Might Be Associated with

Impairments in Those Factors

Factor

I Verbal ProductionII Constructional- Visuospatial

III Verbal Memory

IV Fine Movements

V Verbal Knowledge

VI Praxis AbilityVII Delayed Associative Learning

VIII ArithmeticIX Attentional

Test

Verbal fluencyRey-Osterrieth FigureVisual memory WMSLogical memory

Tapping test

InformationBoston Naming TestIdeomotor apraxia testDelayed AssociativeLearning WMSDigitsMental control WMS

Probable Neuropsychological Syndrome

Convexital left prefrontal syndromeConstructional apraxiaSpatial agnosiaVerbal amnesiaWeroicke aphasiaPremotor syndromeKinetic apraxiaWernicke aphasiaAnomiaIdeomotor apraxiaHippocampal amnesia

AcalculiaOrbital prefrontal syndrome

Table IV. Some Relatively Constant Factors Found Across DifferentFactor- Analytic Studies (Carroll, 1993) and the Neuropsychological

Syndromes with Which They Might Be Associated

Factor

LanguageLexical KnowledgeGrammatical SensitivityCommunication AbilityOral ProductionSpeech Sound DiscriminationNaming FacilityExpressional and Word Fluency

ReasoningSequentialInductiveQuantitative

Visual PerceptionSpatial RelationsSerial Perceptual IntegrationPerceptual Speed

NumericalNumber Facility

Attention and ConcentrationAttention and Concentration

Neuropsychological Syndrome

Wernicke aphasiaBroca aphasiaPrefrontal syndromeVerbal apraxia?Word deafnessAnomiaExtransylvian motor aphasia

Prefrontal syndromePrefrontal syndromeFrontal acalculia

Spatial agnosiaTopographic agnosia?Visual agnosia

Acalculia

Prefrontal syndrome

128 Ardila

left frontal, and bilateral damage. The results demonstratedthat in general, patients with frontal lesions performed aswell as other patients in a variety of intelligence tests.Teuber, however, found deficits in some visuoperceptualtests, such as visual search tasks. These defects in visualsearch have also been pointed out by different authors(e.g., Luria, 1980). Milner (1982) also found impairedperformance in same-different comparisons using clicks,flashes, and colors. Further, she pointed out that frontaldamage patients have difficulties indicating the recencyof an item in a series using either figures or words. Signif-icant difficulties in sequential or temporal memory havebeen observed in this group of patients, and it has evenbeen proposed that the temporality of behavior representsa core defect in cases of frontal pathology (Fuster, 1989).

In traditional psychometric intelligence tests, perfor-mance of frontal damage patients can be normal or nearnormal. Black (1976) found a mean WAIS verbal IQ of99.1 and a mean performance IQ of 99.5 in a group of44 Vietnam veterans who had sustained unilateral frontallobe shrapnel injuries. Janowsky et al. (1989) describedseven patients with various focal frontal lobe lesions whoobtained a mean WAIS-R Full Scale IQ of 101. Damasioand Anderson (1993) analyzed 10 patients with frontal le-sions (ventrolaeral and dorsolateral) caused by either vas-cular events or surgical resection for treatment of tumors.The most notable feature of the WAIS-R testing in thesepatients was the consistent preservation of the cognitiveabilities required to perform the various intellectual tasksfollowing frontal lobe damage.

By the same token, in normal subjects, low corre-lations between traditional intelligence test scores andexecutive function measures have been reported. Welshet al. (1991) observed in children that most of the execu-tive function tasks (Visual Search, Verbal Fluency, MotorPlanning, Tower of Hanoi, Wisconsin Card Sorting Test(WCST), and Matching Familial Figures Test) were un-correlated with IQ. Visual Search, Verbal Fluency, WCST,and Tower of Hanoi did not correlate with any IQ mea-sure (Verbal, Quantitative, and Nonverbal) from the IowaTest of Basic Abilities. Using a 300-subject college stu-dent sample, Ardila et al. (1998) observed that VerbalFluency tests presented a low but significant correlation(about 0.20 to 0.25) with some WAIS verbal subtests, par-ticularly Digits, Arithmetic, and Information. However,WCST scores did not correlate at all with the Verbal, Per-formance, or Full Scale IQ. Ardila etal. (in press) analyzedthe correlation between IQ and some executive functionmeasures (WCST, verbal fluency, and Trial Making Test(TMT), Form A and Form B). Fifty 13- to 16-year-oldnormal children were selected. It was found that verbalfluency tests correlated about 0.30 with Verbal IQ and

Full Scale IQ. In the WCST only Persevertive Errors neg-atively correlated with Verbal IQ and Full Scale IQ. Onlytwo correlations were found to be significant with regard tothe TMT: TMT Form B Errors negatively correlated withWISC-R Vocabulary subtest; and TMT A Time negativelycorrelated with Performance IQ. Results were interpretedas supporting the assumption that traditional intelligencetests are not fully evaluating executive functions.

In general, prefrontal lobe activity has been asso-ciated with self-regulation, control of cognition (meta-cognition), temporal organization of behavior, monitoringof behavior, selective inhibition of responses to immedi-ate stimuli, planning behavior, and control of attention(Brown, 1985;Damasio and Anderson, 1993;Fuster, 1989;Hecaen, 1964; Luria, 1966,1969,1973,1980; Perecman,1987;Pribram, 1973;Stuss and Benson, 1983,1986,1987).These are the abilities not tapped by psychometric intel-ligence tests. The term executive function has been pro-posed to refer to the multi-operational system mediated byprefrontal areas of the brain and their reciprocal corticaland subcortical connecting pathways (Stuss and Benson,1986). Executive dysfunction may be summarized in twocardinal defects: in controlling behavior and in organizingcognition.

Evidently, traditional intelligence tests do not appro-priately evaluate executive function disturbances. It hasto be concluded that either executive functions should notbe included as elements of "intelligent behavior" or psy-chometric intelligence tests are insufficient in testing forintelligence. They are not sensitive to the most impor-tant elements of "intelligence": "To act purposefully" (i.e.,controlling and planning behavior) and "to think ratio-nally" (i.e., organizing and directing cognition) accordingto Wechsler's (1944) definition of intelligence.

The conclusion is evident: psychometric intelligencetests do not appropriately appraise intelligence. Or at least,they are not appraising those abilities that from a neuropsy-chological perspective (and also from the point of view ofthe Wechsler's intelligence testing) should be understoodas the most important elements in intelligence.

Memory and Visuoperceptual Abilities

One of most basic functions of the cerebral cortex isto encode and store new information (memory). One basicarea in assessing cognitive activity refers to memory eval-uation (Lezak, 1995; Spreen and Strauss, 1991). The WISdoes not appropriately measure memory. Wechsler him-self realized the significant shortcoming of his intelligencescale and created a parallel scale directed specifically tomeasure memory (Wechsler Memory Scale; Wechsler,


1945). However, the WIS has remained within the domainof psychometric intellectual measures, whereas theWechsler Memory Scale has been widely used in the neu-ropsychology domain.

It could be argued that some WIS subtests are indeedevaluating memory: the Information subtest measures re-mote memory and Digits measures immediate memory.It is easy to agree with this perspective. However, thereare at least two significant shortcomings in WIS memoryappraisal. (1) The memory process is not evaluated (i.e.,the ability to encode, store, and retrieve new information).This is the most critical type of memory test in neuropsy-chology (e.g., Lezak, 1995; Luria, 1976b). (2) At leastverbal and nonverbal memory testing should be includedin a cognitive evaluation. Evidently, memory assessmentusing the WIS is insufficient, even though WAIS-III hasattempted, at least partially, to overcome this significantshortcoming.

By the same token, WAIS subtests fail to appropri-ately measure spatial and visuoperceptual abilities. In-deed, some WIS subtests partially tap into spatial andvisuoperceptual abilities (e.g., Picture completion). Butit is difficult to accept that WIS subtests are good enoughto evaluate spatial and visuoperceptual abilities. There aremany better tests in the area (see Lezak, 1995).

SOME CONTEMPORARY VIEWS ABOUTINTELLIGENCE

Even though the issue of intelligence has been a"hot" topic for many years, the main questions remainunsettled. Recently, some integrative papers have beenpublished, attempting to distinguish what is really knownand what still remains controversial with regard to intelli-gence. Neisser et al. 's (1996) paper "Intelligence: Knownsand Unknowns" published in American Psychologist rep-resents perhaps the most authoritative report. The paperwas prepared by a task force specifically appointed by theBoard of Scientific Affairs of the American Psychologi-cal Association. Some of the main conclusions presentedby Neisser and his 10 expert co-authors are (1) There aremany ways to be intelligent, and there are also many con-ceptualizations of intelligence. (2) Psychometry has beenable to measure a wide range of abilities that are distinctfrom one another and yet intercorrelated. It is possible todescribe the complex relationships between these abilitiesin many different ways. Some authors have searched for a"general intelligence" (g) factor, whereas others have pre-ferred to refer to a set of independent factors. Still othershave opted for a hierarchy of factors. (3) Intelligence iscorrelated with school achievement at a level of about 0.50

(some 25% of the variance). (4) Like every trait, intelli-gence is the joint product of genetic and environmentalfactors. (5) School affects intelligence in many differentways: transmitting specific information, developing cer-tain skills and attitudes. Failure to attend school has neg-ative consequences in intelligence testing. (6) Some bi-ological conditions have clear negative consequences onintelligence. Examples are perinatal complications, expo-sure to environmental lead, and exposure to high bloodlevels of alcohol. (7) There is a steady rise across timein intelligence test scores known as the "Flynn effect"(Flynn, 1984,1987). Mean IQ scores have increased morethan 15 points in the last 50 years. Some reasons may beimproved nutrition, cultural changes, experience with test-ing, shifts in schooling or child-rearing practices, or someother unknown factors. (8) Ethnic differences in intelli-gence reflect complex patterns. No overall generalizationabout them is appropriate. (9) Many of the most criticalquestions about intelligence remain unanswered.

Some brief comments may be presented to theseselected conclusions: (1) Evidently, the concept and in-terpretation of intelligence continue to be controversial.Neisser et al. (1996) recognized that there are differentways to interpret intelligence. No single interpretation ofintelligence testing data is widely accepted, (2) Neisseretal. (1996) refer to the bidirectional relationship betweenschool and IQ: intelligence predicts school achievement,and school affects intelligence. (3) Many factors may be si-multaneously acting on the scores obtained in intelligencetests: genetic factors, some early biological conditions, en-vironmental factors, cultural values, etc. (4) Given the so-called flynn effect, several factors may be simultaneouslyinteracting to cause the recent rapid rise in test scores. Fora person coming from a nonpsychometrically oriented cul-ture (as the author of this paper), however, it is evident thatthe most crucial factor may be the tremendous training intesting abilities that Americans have been progressivelyexposed to. Although exposure to psychometric testinghas extended to other countries, it is markedly higher inthe United States than in most countries. School childrencurrently spend a significant amount of time developingthose strategies required in answering tests, and in prac-ticing tasks similar to those included in intelligence tests.This was not observed one generation ago. (5) No gener-alization or general conclusion about ethnic differences inintelligence is acceptable. There are many ways to be in-telligent in different cultural contexts. Good performanceon psychometric intelligence tests is just one way to beintelligent in a quite specific cultural context.

Reactions to Neisser et al.'s (1996) paper rapidly ap-peared (see American Psychologist, 52(1), 1997). Reac-tions were so mixed that the only conclusion that can be

130 Ardila

safely drawn is that intelligence continues as a very contro-versial and, in many regards, a poorly understood topic.If a conservative paper like that of Neisser el al. couldtrigger so many different and opposite reactions, it mustbe concluded that the concept of intelligence is on veryfragile ground.

WHAT SHOULD BE INCLUDED WHENTESTING FOR COGNITIVE ABILITIES?

Since Thurnstone (1938,1947), there is the converg-ing consensus that some fundamental cognitive abilitiesmay be distinguished. Researchers refer to a limited num-ber of domains, usually six to nine, frequently appearingin factor analytic studies of psychological (Carroll, 1993)and neuropsychological test batteries (Ardila etal., 1994,1998; Pont6n et al., 1994). A similar idea is presented byGardner (1983) when he proposed different types of in-telligence. Evidently, these are the cognitive domains thatshould be included when testing for intellectual abilities.There are no fixed tests to evaluated these domains, eventhough some tests may be better, at least at a certain his-torical moment. In the future, new and better tests can bedeveloped to appraise these domains, and these domainsmay even be restated and rearranged.

In neuropsychology there are several tests that havebecome widely accepted and extensively used (see Lezak,1995; Spreen and Strauss, 1998). They are considered re-liable, sensitive, and in general "good" tests. There is asignificant research body supporting their reliability andvalidity. An evaluation of cognitive abilities should in-clude these widely accepted tests. As a matter of fact,many of them have been taken from the intelligence test-ing research, and in this regard, psychometric intelligencetesting and neuropsychological testing may be comple-mentary rather than mutually exclusive. Of course, it is ex-pected that in the future, superior testing instruments willbe developed, replacing the current tests that now are con-sidered the best available neuropsychological instruments.

Examples of these cognitive domains, and potentiallyuseful tests are:

1. Attention

1.1. Focused attention (e.g., digits backwards)1.2. Sustained attention (e.g., serial subtractions

etc.)

2. Language

2.1, Verbal fluency (using semantic and phonolog-ical categories)

2.2. Language comprehension (token test)

2.3. Lexical knowledge (naming, vocabulary, orother similar tests)

3. Calculation abilities

3.1. Arithmetical operations3.2. Numerical problems

4. Perceptual abilities

4.1. Visual recognition of figures under differentconditions (e.g., visual detection, to recognizeembedded or unusually presented figures, tofind similarities and differences between fig-ures, etc.)

4.2. Recognition of sounds and music (verbal-pho-nological discrimination; and nonverbal rhy-thms, melodies, music, etc.)

5. Memory and learning

5.1. Verbal learning (Serial Verbal Learning, Cali-fornia Verbal Learning Test, Rey AuditoryVerbal Learning test, Logical Memory, etc.)

5.2. Nonverbal learning (Benton Visual Retentiontest, immediate and delayed recall of figures)

6. Visuoconstructive and visuospatial abilities

6.1. Visuoconstructive (such as Rey-OsterriethComplex Figure)

6.2. Tests for spatial abilities (such as line orienta-tion)

7. Motor

7.1. Fine movements (such as the Finger TappingTest or other fine movements test)

7.2. Praxis ability tests

8. Executive function abilities

8.1. Abstraction (e.g., Similarities)8.2. Reasoning (e.g., Raven Progressive Matrixes)8.3. Concept formation tests (the Category Test,

Wisconsin Card Sorting Test, etc.)8.4. Some tests directed to "maintain instructions"

(Stroop test, Trial Making Test Form B, Luria'sopposite reactions, etc.)

Of course, these tests are not necessarily evaluatinga single cognitive domain. Attention is required for anappropriate performance in any intellectual test. Calcula-tion abilities represent a rather complex and multifactorialability. Verbal memory depends on language understand-ing. For example, phonological verbal fluency can be in-terpreted as an executive function test, whereas semanticverbal fluency is closer to a lexical knowledge test. Fur-thermore, all these tests are significantly influenced byeducation, age, and cultural background. Norms for dif-ferent groups should be obtained. Although raw scorescan be nonequivalent in different educational, cultural,

Intelligence and Neuropsychology

and age groups, standard normalized scores are equiva-lent. Each group itself represents its own norm. Tests mustbe standardized and norms obtained not only for differentage ranges but also for different educational and culturalgroups. Otherwise, what is normal for one group might beinterpreted as pathological for another. When a particu-lar group outscores another, this simply means that wrongnorms have been used.

THE WAIS-III

In the last 50 years, the same 11 subtests proposed byWechsler in the 1930s were repeated over and over again,with just minor changes. Not until 1997 were some fun-damental changes introduced to the WIS. The WAIS-III(Wechsler, 1997) represents a very significant improve-ment over previous versions. But changes are far fromenough.

The WAIS-III includes some new subtests directedto overcome some of the limitations found in the previousWIS versions: Instead of 11 subtests, there are 14 (sevenverbal subtests and seven performance subtests) used tocalculate IQs. In the Verbal Scale, the Letter-Number Se-quencing subtest (combinations of numbers and letters areread and the examinee is required to recall the numbersfirst in ascending order and then letters in alphabetical or-

der) is added. In the Performance Scale Matrix, Reasoning(the examinee looks at a matrix from which a section ismissing and either identifies the number or points to oneof five response options that completes the matrix) andSymbol Search (the examinee visually scans two groupsof symbols, a target group composed of two symbols anda search group composed by five symbols, and indicateswhether either target symbol matches any of the symbolsin the search group) were added. The Digit-symbol subtestis used under different conditions: Digit symbol-Coding(as previously used), Digit symbol-Incidental Learning(paring to recall the symbols matched with the numbers,and free recall to recall the symbols used in coding sec-tion), and Digit symbol-Copy (to copy the symbols thatwere used in the Digit symbol-Coding). These two lastconditions are optional and are not used in calculatingIQs. Table V presents the cognitive domains and areasincluded in the WAIS-III subtests.

Several major concerns arise: (1) Testing for cogni-tive abilities is still insufficient (see above); (2) It is noteasy to understand why if several factor analyses disclosedfour different factors (Verbal Comprehension, PerceptualOrganization, Working Memory, and Processing Speed),the WAIS-III insists on calculating only two compoundscores (Verbal and Performance) instead of four. In thedifferent factor analytic studies that are presented in theWAIS-III Technical Manual, the Object Assembly subtest

131

Table V. Cognitive Domains and Areas Included in the WAIS-III Subtests.

Cognitive Domain

1. Attention

2. Language

3. Calculation abilities

4. Perceptual abilities

5. Memory

6. Visuoconstructiveand visuospatial

7. Motor

8. Executive functions

Area

Focused attentionSustained attentionFluencyLanguage comprehensionLexical knowledgeArithmetical operationsNumerical problemsVisual recognition

Auditory recognitionVerbal learningNonverbal learningVisuoconstructive

Spatial abilitiesFine movementsPraxisAbstractionReasoningConcept formation"Maintain instructions"

WAIS-OI Subtest

Digit spanDigit-symbolNot includedNot includedVocabularyNot includedArithmeticsPicture completionSymbol searchNot includedNot includedDigit-symboI-ILBlock DesignObject AssemblyNot includedNot includedNot includedSimilaritiesMatrix reasoningNot includedLetter-number

Factora

Working MemoryProcessing Speed

Verbal Comprehension

Working MemoryPerceptual OrganizationProcessing Speed

Perceptual Organization

Verbal Comprehensionb

Perceptual Organization

Working Memory

aFactors found in the WAIS-III (Wechsler, 1997).bComprehension is a subtest difficult to interpret and includes two different types of subtests (proverb interpretation andknowledge of social conventions).

132 Ardila

was not included. No reason for this exclusion is men-tioned. (3) Scores are corrected according to age but notaccording to educational level, although the most impor-tant variable affecting psychological and neuropsycholog-ical test performance is education, not age (e.g., Anastasi,1988; Cronbach, 1990; Ostrosky et al., 1998). Neverthe-less, raw scores should be corrected by both education andage. In the standardization sample used, about two thirdsof the subjects had 12 or more years of education. Thelowest educational group included in the normative sam-ple had "eight or less years of education," which is mostlikely an inappropriate education cut-off point (Ostroskyet al., 1998). The WAIS-III seems inappropriate to testpeople with low educational levels. (4) The WAIS-III re-tains the total compound score (Full Scale IQ) despitethe fact that the factor analytic studies presented in theWAIS-III Technical Manual show that the four factorsobtained in the different factor analyses are rather inde-pendent.

In brief, the WAIS-III is undoubtedly an improve-ment over previous WIS versions. This is the first timethat Wechsler's original testing schema has been, at leastpartially, abandoned, and new tests are included. After al-most 50 years of extensive use, it was finally acceptedthat the 11 WIS subtests proposed by Wechsler were in-sufficient to test cognitive abilities. Evidently, WAIS-IIIrepresents an implicit recognition that at least executivefunctions and memory had been insufficiently tested in theWIS previous versions. Nonetheless, it does not mean thatnew WAIS-III has overcome the major difficulties pointedout above, and no research studies using the WAIS-III areyet available.

COGNITIVE ABILITIES EN DIFFERENTCULTURAL CONTEXTS

Psychometric intelligence tests have been developedin a very specific cultural context. They rely on those abil-ities that are significant in that particular cultural contextand on those approaches that are culturally most valuable.

In neuropsychology, cognitive disturbances associ-ated with brain pathology of a very limited subsampleof the human species—contemporary Western, and mostoften, urban middle-class, and literate brain-damagedindividuals—have been relatively well analyzed. Our un-derstanding about the brain's organization of cognitiveabilities, and their disturbances in cases of brain pathol-ogy, is therefore not only partial but, undoubtedly, cul-turally biased. Cultural and linguistic diversity is an enor-mous, but frequently overlooked, moderating variable.Several thousand different cultures have been described by

anthropology (e.g., Bernatzik, 1957), and contemporaryhumans speak over 4,000 different languages (Swadesh,1967). Evidently, an extended analysis of cognitive dis-turbances in different cultural and ecological contexts isnecessary for us to understand and serve the neuropsycho-logical needs of our constituency.

Supposedly, comparable fundamental cognitive dis-turbances are to be found in every human species mem-ber, regardless of cultural background, educational level,language, and ecological demands, as a consequence ofbrain lesions. There are some fundamental characteris-tics in the human brain, and in brain-behavior relation-ships that one would expect to observe in every humansubject. Basic cognitive processes are universal, and cul-tural differences in cognition reside more in the situationsto which particular cognitive processes are applied thanin the existence of the process in one cultural group andthe absence in another. Culture prescribes what should belearned and at what age. Consequently, different culturalenvironments lead to the development of different patternsof abilities. Cultural and ecological factors play a role indeveloping different cognitive styles (Berry, 1971,1979).Furthermore, cultural variables can eventually influencethe brains' organization of cognition. For example, it hasbeen reported that the degree (not the direction) of brainlateralization of language can depend on literacy, and ingeneral, on the verbal training histories (Lecours et al.,1987,1988; Matute, 1988).

Language, memory, visuospatial abilities, praxisskills, and cognitive abilities in general studied in psychol-ogy and neuropsychology are under cultural influence.Cognitive disturbances associated with brain pathologyare related to the way those abilities have been trained.Brain damage results in the disturbance in a specific levelof information processing, even though the actual manifes-tation depends on the specific pattern of cognitive abilities.This specific pattern of cognitive abilities is culturally de-pendent. Reading and writing can illustrate the enormouscomplexity of brain organization of any cognitive process.Supposedly, reading is based on certain fundamental abil-ities (e.g., complex shape perception, cross-modal learn-ings, etc.) already existing 5,000 years ago in preliteratehumans, and of course, existing in illiterate individuals.The human brain might be specialized not for reading orwriting per se, but for certain basic abilities (informationprocessing levels or cognition factors) required to read andto write, albeit not only to read or to write. It does not seemreasonable to assume that some brain areas are specializedin reading or writing, just as it does not seem reasonableto suppose that some brain areas are specialized in usingcomputers. Even though the fundamental defect may bethe same, the actual manifestation of brain pathology may


be different depending on the training histories and theactual pattern of cognitive abilities.

If, despite some existing basic characteristics in itsbrain organization, oral and written language disturbancesare associated with language idiosyncracies (e.g., apha-sia is not completely equivalent in Chinese and Spanish;alexia and agraphia can be different in English, Span-ish, and Japanese, etc.; Ardila etal., 1996; Sasanuma andFujimura, 1971; Yamadori, 1975; Yu-Huan etal., 1990),other cognitive abilities such as spatial cognition may alsodepend on the specific ability learning history and the par-ticular cognitive style. Supposedly, similar spatial cog-nition disturbances are to be found in a similar way inevery human species member, regardless of the culturalbackground and the ecological demands. Basic spatialcognition abilities, however, are applied in rather differ-ent ways depending on the specific cultural context andthe ecological demands. Contemporary city individual'sspatial abilities are not necessarily inferior (or superior)to the Eskimos' or Amazonian Indians' spatial abilities.Spatial abilities may have evolved with new living and cul-tural conditions. Spatial cognition abilities can be requiredin many contemporary, and historically recent skills, notfound in every human group. The author of this paperhad the opportunity to study a university chemistry pro-fessor who suffered a small right-parietal infarction with-out any overt spatial disturbance. Although she had notany evident spatial difficulty in her everyday activities,she could not continue teaching chemistry, because shewas "unable to have a spatial representation of moleculesand all the time got confused." Mathematics (Ardila andRosselli, 1990; Luria, 1980), painting, chemistry, chess(Chabris and Hamilton, 1992), reading and writing (Ardilaand Rosselli, 1993; Benson and Ardila, 1996), mechanics(Benton, 1989), and even music (Henson, 1985) all rep-resent, at least partially, spatially based skills. They canbe impaired in cases of right hemisphere damage of thosesame areas that in an Eskimo or Amazonian Indian wouldimply an impossibility to move around the snow or thejungle.

The analysis of cognitive disturbances associatedwith brain pathology in different cultural contexts, nodoubt, represents a challenge for 21st century neuropsy-chology. This analysis may eventually allow researchers tohave a better understanding of the basic elements (factors)of cognition.

SOME TENTATIVE CONCLUSIONS

1. Psychometric intelligence tests (e.g., WIS in itsdifferent versions) do not seem to measure what from

a neuropsychological perspective (and also according toWechsler himself) could be better interpreted as "intel-ligence." At the least, they fail in appraising some mostfundamental aspects.

2. The concept of IQ might disappear. It is archaic,and theoretically remains a controversial concept. Subtestsused to measure "intelligence" are inappropriate.

3. In the future, cognitive evaluation may rely onneuropsychological instruments instead of using psycho-metric intelligence tests. Neuropsychological tests havea clear and overt rationale from the point of view of thebrain organization of cognitive activity. No clear rationalfor the WIS subtests is easily found.

4. It would seem more appropriate to use standardscores (such as T, z, or percentiles) for the individualtests and cognitive domains, than using global intellec-tual scores (such as IQ).

ACKNOWLEDGMENTS

My most sincere gratitude to Virginia Standish for hermost valuable support and help while preparing this paper.Thanks to Dr. Kevin Keating, Dr. Mariano Alemagny, andDr. Sarah Ransdell for their observations and suggestionson this paper. My gratitude to the anonymous reviewersfor their most helpful, encouraging, and interesting obser-vations.

REFERENCES

Anastasi, A. (1988). Psychological Testing (6th ed.), MacMillan, NewYork.

Ardila, A. (1995a). Directions of research in cross-cultural neuropsy-chology. Journal of Clinical and Experimental Neuropsychology17:143-150.

Ardila, A. (1995b). Estructura de la actividad cognoscitiva: Hacia unateoria neuropsicologica [Structure of cognitive activity: Towarda neuropsychological theory]. Neuropsychologia Latina 1(2): 21-32.

Ardila, A., Galeano, L. M., and Rosselli, M. (1998). Toward a model ofneuropsychological activity. Neuropsychology Review 8:171-190.

Ardila, A., Pineda, D., and Rosselli, M. (in press). Correlation betweenintelligence test scores and executive function measures. Archivesof Clinical Neuropsychology.

Ardila, A., and Rosselli, M. (1990). Acalculias. Behavioural Neurology3:39-48.

Ardila, A., and Rosselli, M. (1993). Spatial agraphia. Brain and Cogni-tion 22: 75-95.

Ardila, A., and Rosselli, M. (1994). Development of language, mem-ory and visuospatial abilities in 5- to 12-year-old children using aneuropsychological battery. Developmental Neuropsychology 10:97-120.

Ardila, A., Rosselli, M., and Bateman, J. R. (1994). Factorial structureof cognitive activity. Behavioral Neurology 7:49-58.

Ardila, A., Rosselli, M., and Ostrosky, F. (1996). Agraphia in Spanish-language. Aphasiology 10: 723-739.

134 Ardila

Benson, D. F. (1982). The alexia: A guide to the neural basis of reading.In Kirsher, H. S., and Freemon, F. (eds.), The Neurology of Aphasia,Swets, Amsterdam, pp. 139-161.

Benson, D. F. (1994). The Neurology of Thinking, Oxford UniversityPress, New York.

Benson, D. F., and Ardila, A. (1996). Aphasia: A Clinical Perspective,Oxford University Press, New York.

Benton, A. (1989). Constructional apraxia. In Goodglass, H., andDamasio, A. R. (eds.). Handbook of Clinical Neuropsychology(Vol. 2), Elsevier, Amsterdam, pp. 287-294.

Bernatzik, H. A. (1957). Razas y pueblos del mundo [World races andpeople]. Vols. 1-3. Ediciones Ave, Barcelona.

Berry, J. W. (1971). Ecological and cultural factors in spatial perceptualdevelopment. Canadian Journal of Behavioral Sciences 3: 324-336.

Berry, J. W. (1979). Culture and cognition style. In Mrsella, A., Tharp,R. G., and Ciborowski, T. J. (eds.). Perspectives in Cross-CulturalPsychology, Academic Press, New York, pp. 117-135.

Berry, J. W., Poortinga, Y. H., Segall, M. H., and Dasen, P. R.(1992). Cross-Cultural Psychology, Cambridge University Press,Cambridge.

Binet, A. (1905). Analysis of C.E. Spearman: The proof and measure-ment of association between two things and general intelligenceobjectively determined and measured. L'Anne Psychologique 11:623-624.

Binet, A. (1908). Le developpement de 1'intelligence chez les en-fants. [The development of intelligence in children.] L'AnnePsychologique 14:1-94.

Black, F. W. (1976). Cognitive deficits in patients with unilateralwar-related frontal lobe lesions. Journal of Clinical Psychology32: 366-372.

Bornstein, R. A., and Chelune, G. J. (1988). Factor structure of theWechsler Memory Scale-Revised. The Clinical Neuropsychologist2:107-115.

Brazzelli, M., Colombo, N., Delia Salla, S., and Spinnler, H. (1994).Spared and impaired abilities after bilateral frontal damage. Cortex30: 27-51.

Brody, N. (1992). Intelligence (2nd ed.). Academic Press, New York.Brown, J. E. (1985). Frontal lobe syndromes. In Frederiks J. A.

M. (ed.), Handbook of Clinical Neurology, Vol. 45: ClinicalNeuropsychology, Elsevier, Amsterdam, pp. 32-41.

Carroll, J. B. (1993). Human Cognitive Abilities: A Survey of FactorAnalytic Studies, Cambridge University Press, Cambridge.

Cattell, R. B. (1971). Abilities: Their Structure, Growth and Action,Houghton-Mifflin, Boston.

Ceci, S. J. (1990). On Intelligence... More or Less: A BioecologicalTreatise on Intellectual Development, Prentice Hall, Englewood,NJ.

Ceci, S. J. (1991). How much does schooling influence general intelli-gence and its cognitive components? A reassessment of evidence.Developmental Psychology 27:703-722.

Ceci, S. J., and Williams, W. M. (1997). Schooling, intelligence andincome. American Psychologist 52:1051-1058.

Chabris, C. F., and Hamilton, S. E. (1992). Hemispheric special-ization for skilled perceptual organization by chessmasters.Neuropsychologia 30:47-57.

Cronbach, L. J. (1990). Essentials of Psychological Testing (5th ed.),Harper and Row, New York.

Damasio, A. R., and Anderson, S.W. (1993). The frontal lobes. In Heil-man, K. M., and Valenstein, E. (eds.), Clinical Neuropsychology,Oxford University Press, New York, pp. 409-460. 3rd edition.

Damasio, H., and Damasio, A. R. (1989). Lesion Analysis in Neuropsy-chology, Oxford University Press, New York.

Das, J. P., Naglieri, J. A., and Kirby, J. R. (1994). Assessment ofCognitive Processes: The PASS Theory of Intelligence, Allyn &Bacon, Needham Heights, MA.

De Renzi, E. (1982). Disorders of Space Exploration and Cognition,Wiley, New York.

De Renzi, E. (1985). Disorder of space exploration. In Frederiks,

J. A. M. (ed.), Handbook of Clinical Neurology, Vol. 45: ClinicalNeuropsychology, Elsevier, Amsterdam, pp. 405-422.

Elwood, R. W. (1991). Factor structure of the Wechsler MemoryScale-Revised (WMS-R) in a clinical sample: A methodologicalreappraisal. The Clinical Neuropsychologist 5:329-337.

Eysenck, H. (1986). Inspection time and intelligence: A historicalintroduction. Personality and Individual Differences 7:603-607.

Flynn, J. R. (1984). The mean IQ gains of Americans: Massive gains1932-1978. Psychological Bulletin 95:29-51.

Flynn, J. R. (1987). Massive IQ gains in 14 nations: What IQ tests reallymeasure. Psychological Bulletin 101:171-191.

Frearson, W. M., and Eysenck, H. J. (1986). Intelligence, reaction time[TR] and a new "odd-man-out" RT paradigm. Personality andIndividual Differences7: 807-817.

Fuster, J. M. (1989). The Prefrontal Cortex (2nd ed.), Raven Press, NewYork.

Gardner, H. (1983). Frames of Mind: The Theory of Multiple Intelli-gences, Basic Books, New York.

Greenfield, P. M. (1997). You can't take it with you: Why ability as-sessments don't cross cultures. American Psychologist 52: 1115-1124.

Guilford, J. P. (1967). The Nature of Human Intelligence, McGraw-Hill,New York.

Guilford, J. P. (1968). Intelligence has three facets. Science 160:615-620.

Guilford, J. P., and Hoepfner, R. (1971). The Analysis of Intelligence.McGraw-Hill, New York.

Hebb, D. (1939). Intelligence in man after large removals of cerebraltissue: Report of four left frontal lobe cases. Journal of GeneralPsychology 21:73-87

Hebb, D. O. (1942). The effects of early and late brain injury upon testscores and the nature of normal adult intelligence. Proceedings ofthe American Phylosophical Society 85:275-292.

Hebb, D. O. (1945). Man's frontal lobe: A critical review. Archives ofNeurology and Psychiatry 54:421-438.

Hebb, D., and Penfield, W. (1940). Human behavior after extensivebilateral removal from the frontal lobes. Archives of Neurologyand Psychiatry 44: 421-438.

Hecaen, H. (1962). Clinical symptomatology in right and left hemi-sphere lesions. In Mountcastle, V. B. (ed.), InterhemisphericRelations and Cerebral Dominance, John Hopkins University,Baltimore, pp. 215-243.

Hecaen, H. (1964). Mental symptoms associated with tumors of thefrontal lobe. In Warren, J. M., and Akert, K. (eds.), The FrontalGranular Cortex and Behavior, McGraw-Hill, New York, pp.335-352.

Hecaen, H., and Albert, M. L. (1978). Human Neuropsychology, Wiley,New York.

Henson, R. A. (1985). Amusia. In Frederiks, J. A. M. (ed.), Handbookof Clinical Neurology, Vol. 45: Clinical Neuropsychology, Elsevier,Amsterdam, pp. 483-490.

Hunter, J. (1986). Cognitive ability, cognitive aptitudes, job knowledge,and job performance. Journal of Vocational Behavior 29: 340-363.

Irvine, S. H., and Berry, J. W. (eds.), (1988). Human Ability in CulturalContext, Cambridge University Press, Cambridge.

Janowsky, J. S, Shimamura, A. P., Kritchevsky, M., and Squire, L. R.(1989). Cognitive impairments following frontal lobe damage andits relevance to human amnesia. Behavioral Neurosciences 103:548-560.

Jensen, A. R. (1980). Bias in mental testing. Free Press, New York.Jensen, A. R. (1987). Individual differences and the Hick paradigm. In

P. A. Vernon (ed.), Speed of Information Processing and Intelli-gence, Ablex, Norwood, pp. 101-175.

Kaiser, H. F. (1960). The varimax solution for Primary Mental Abilities.Psychometrika 25:153-158.

Kaplan, E., Fein, D., Morris, R., and Delis, D. (1991). WAIS-R as aNeuropsychological Instrument, Psychological Corporation, SanAntonio. TX.


Kaufman, A. S., and Kaufman, N. L. (1993). Manual for the KaufmanAdolescent and Adult Intelligence Test (KAIT), American GuidanceService, Circle Pines, MN.

Kaufman, A. S., and Kaufman, N. L. (1997). The Kaufman Adolescentand Adult Intelligence Test. In Flanagan, 0. P., Genshaft, J. D.,and Harrison, P. L. (eds.), Contemporary Intellectual Assessment:Theories, Tests and Issues, Guilford Press, New York, pp. 209-229.

Kertesz, A. (1983). Localization in Neuropsychology, Academic Press,New York.

Lecours, A. R., Mehler, J., Parente, M. A., Beltrami, M. C, Canossade Tolipan, L., Castro M. J., Carrono, V., Chagastelles, L., Dehaut,P., Delgado, R., Evangelista, A., Fajgenbaum, S., Fontoura, C.,de Fraga Karmann, D., Gurd, J., Hierro Tome, C., Jakubovicz, R.,Kac, R., Lefevre, B., Lima, C., Maciel, J., Mansur, L., Martinez,R., Nobrega, M. C., Osorio, Z., Paciomik, J., Papaterra, P.,Jourdan Penedo, M. A., Saboya, B., Scbeuer, C., Batista da Silva,A., Spinardi, M., and Texeira, M. (1988). Illiteracy and braindamage. III: A contribution to the study of speech and languagedisorders in illiterates with unilateral brain damage (initial testing).Neuropsychohgia 26:575-589.

Lecours, R. L., Mehler, J., Parente, M. A., Caldeira, A., Cary, L.,Castro, M. J., Dehaout, P., Delgado, R., Gurd, J., Karmann, D.,Jakubovitz, R., Osorio, Z., Cabral, L. S,, and Junqueira, M. (1987).Illiteracy and brain damage, I: Aphasia testing in culturally con-trasted populations (control subjects). Neuropsychohgia 25: 231-245.

Lezak, M. D. (1995). Neuropsychological Assessment (2nd ed.), OxfordUniversity Press, New York.

Luria, A. R. (1966). Human Brain and Psychological Processes, Harperand Row, New York.

Luria, A. R. (1969). Frontal lobe syndromes. In Vinken, P. J., andBruyn, G. W. (eds.), Handbook of Clinical Neurology, Vol. 2,North Holland, Amsterdam, pp. 725-757.

Luria, A. R. (1973). The frontal lobes and the regulation of behavior.In Pribram, K. H., and Luria, A. R. (eds.), Psychophysiology of theFrontal Lobes, Academic Press, New York, pp. 3-26.

Luria, A. R. (1976a). Basic Problems ofNeurolinguistics, Mouton, TheHague, Netherlands.

Luria, A. R. (1976b). The Neuropsychology of Memory, Halstead,Somerset, NJ.

Luria, A. R. (1980). Higher Cortical Functions in Man (2nd ed.), Basic,New York.

Matarazzo, J. D. (1972). Wechsler's Measurement and Appraisal ofAdult Intelligence, Oxford University Press, New York.

Matute, E. (1988). El aprendizaje de la lectoescritura y laespecializacionhemisferica para el lenguaje [Reading and writing learning, andhemispheric specialization for language]. In Ardila, A., andOstrosky-Solis, F. (eds.), Lenguaje oral y escrito [Oral and writtenlanguage]. Mexico D. F., Mexico: Editorial Trillas, pp. 310-358.

Milner, B. (1963). Effects of different brain lesions on card sorting.Archives of Neurology 9:90-100.

Milner, B. (1982). Some cognitive effects of frontal-lobe lesions inman. Philosophical Transactions of the Royal Society of London298:211-226.

Morrow, L., and Ratcliff, G. (1988). The neuropsychology of spatialcognition. In Stiles-Davis, J., Kritchevsky, M., and Bellugi, U.(eds.), Spatial Cognition: Brain Bases and Development, Erlbaum,Hillsdale, NI, pp. 5-32.

Naglieri, J. A. (1997). Planning, attention, simultaneous and succesivetheory and the cognitive assessment system: A new theory-basedmeasure of intelligence. In Flanagan, D. P., Genshaft, J. D., andHarrison, P. L. (eds.), Contemporary Intellectual Assessment:Theories, Tests and Issues, Guilford Press, New York, pp. 247-267.

Naglieri, J. A., and Das, J. P. (1996). Das Naglieri Cognitive AssessmentSystem, Riverside, Chicago.

Neisser, U., Boodoo, G., Bouchard, T. J., Boykin, A. W., Brody, N.,Ceci, S. J., Halpern, D. R, Loehlin, J. C, Perloff, R.. Stenberg,R. J., and Urbina, S. (1996). Intelligence: Knowns and unknowns.American Psychologist 51:77-101.

Nettlebeck, T. (1987). Inspection time and intelligence. In Vernon,P. A. (ed.), Speed of Information Processing and Intelligence,Ablex, Norwood, NJ, pp. 295-346.

Newcombe, P., and Ratcliff, G. (1989). Disorders of visuospatial anal-ysis. In Goodglass, H., and Damasio, A. R. (eds.), Handbook ofClinical Neuropsychology (Vol. 2), Elsevier, Amsterdam, pp. 333-356.

Ostrosky, F, Ardila, A., and Rosselli, M. (1998). Neuropsychologicaltest performance in illiterates. Archives of Clinical Neuropsychol-ogy 13:645-660.

Ostrosky, F., Ardila, A., and Rosselli, M. (1999). NEUROPSI: A briefneuropsychological test battery in Spanish with norms by age andeducational level. Journal of the International NeuropsychologicalSociety 5:413-433.

Perecman, E. (1987). Consciousness and the meta-functions of thefrontal lobes. In Perecman, E. (ed.). The Frontal Lobes Revisited,IRBN Press, New York, pp. 1-10.

Pettersen, S. E., Fox, P. T, Snyder, A. Z., and Raichle, M. E. (1989).Activation of extrastriate and frontal cortical areas by visual wordsand word-like stimuli. Science 249:1041-1044.

Pirozzolo, F. J. (1985). Mental retardation. In Frederiks, J. A. M.(ed.) Handbook of Clinical Neurology, Vol. 46: NeurobehavioralDisorders, Elsevier, Amsterdam, pp. 1-40.

Ponton, M. O., Satz, P., and Herrera, L. (1994). Factor analysis of aneuropsychological screening battery for Hispanics (NeSBHIS).XVII European Meeting of the International NeuropsychologicalSociety, June.

Posner, M. I., Petersen, S. E., Fox, P. T., and Raichle, M. E. (1988).Localization of cognitive operations in the human brain. Science240:1627-1631.

Pribram, K. H. (1973). The primate frontal cortex—Executive of thebrain. In Pribram, K. H., and Luria, A. R. (eds). Psychophysiologyof the Frontal Lobes, Academic, New York, pp. 293-314.

Price, C. J., Wise, R. J. S., Watson. J. D. G., Patterson, K., Howard, D.,and Frackowiak, R. S. J. (1994). Brain activation during reading:The effects of exposure duration and task. Brain 117:1255-1269.

Reed, T. E., and Jensen, A. R. (1992). Conduction velocity in a brainnerve pathway of normal adults correlates with intelligence level.Intelligence 16: 259-272.

Roid, G. H., Prifitera, A., and Ledbetter, M. (1988). Confirmatory analy-sis of the factor structure of the Wechsler Memory Scale-Revised.Clinical Neuropsychology 2: 116-120.

Rosselli, M., and Ardila, A. (1989). Calculation deficits in patients withright and left hemisphere damage. Neuropsychohgia 27: 607-617.

Sasanuma, S., and Fujimura, O. (1971). Kanji versus Kana processingin alexia with transient agraphia: A case report. Cortex 7:1-18.

Spearman, C. (1904). "General intelligence" objectively determinedand measured. American Journal of Psychology 15:201-293.

Spearman, C. (1923). The Nature of "Intelligence" and the Principlesof Cognition, MacMillan, London.

Spreen, O., and Strauss, E. (1991). A Compendium of Neuropsycholog-ical Tests, Oxford University Press, New York.

Spreen, O., and Strauss, E. (1998). A Compendium of Neuropsycho-logical Tests: Administration, Norms and Commentary (2nd ed.),Oxford University Press, New York.

Stern, W. (1912). Die psychologischen Methoden der Intelligenz pru-fung. [The Psychological Method to Measure Intelligence.] Leipzig:Barth.

Sternberg, R. J. (1985). Beyond IQ: A Triarchic Theory of HumanIntelligence, Cambridge University Press, New York.

Sternberg, R. J. (1988). A triarchic view of intelligence, In Irvine,S. H., and Berry, J. W. (eds.), Human Ability in Cultural Context,Cambridge University Press, New York, pp. 60-85.

Sternberg, R. J. (1997). The concept of intelligence and its role in life-long learning and success. American Psychologist 52:1030-1037.

Stuss, K. H., and Benson, D. F. (1983). Frontal lobe lesions andbehavior. In Kertesz, A. (ed.), Localization in Neuropsychology,Academic Press, New York, pp. 429-454.

136 Ardila

Stuss, D. T, and Benson, D. F. (1986). The Frontal Lobes, Raven Press,New York.

Stuss, D. T., and Benson, D. P. (1987). The frontal lobes and control ofcognition and memory. In Perecman, E. (ed.), The Frontal LobesRevisited, IRBN Press, New York, pp. 141-158.

Swadesh, M. (1967). El Lenguaje y la Vtda Humana [Language andHuman Life], Fondo de Cultural Economica, Mexico.

Terman, L. M. (1916). The Measure of Intelligence, Houghton-Mifflin,Boston.

Teuber, H. L. (1972). Unity and diversity of frontal lobe function. ActaNeurobiology Experimental 32:615-656.

Thorndike, R. L., Hagen, E. P., and Sattler, J. M. (1986). Stanford-Binet Intelligence Scale: Guide for Administration and Scoring,Riverside, Chicago.

Thurnstone, L. L. (1938). Primary Mental Abilities, University ofChicago Press, Chicago.

Thurnstone, L. L. (1947). Multiple Factor Analysis, University ofChicago Press, Chicago.

Vernon, P. E. (1950). The Structure of Human Abilities, Wiley, New York.Wechsler, D. (1944), The Measurement of Adult Intelligence. Williams

and Wilkins, Baltimore.Wechsler, D. (1945). A standardized memory scale for clinical use.

Journal of Psychology 19: 87-95.Wechsler, D. (1987). Manual for the Wechsler Memory Scale-Revised,

Psychological Corporation, San Antonio, TX.Wechsler, D. (1997). WAIS-III: Administration and Scoring Manual,

Psychological Corporation, San Antonio, TX.Welsh, M. C., Pennington, B. F., and Groisser, D. B. (1991). A normative-

developmental study of executive function: A window on prefrontalfunction in children. Developmental Neuropsychology 7: 131-149.

Yamadori, A. (1975). Ideogram reading in alexia. Brain 98: 231-238.

Yu-Huan, H., Ying-Guan, Q., and Gui-Qing, Z. (1990). Crossed aphasiain Chinese: A clinical survey. Brain and Language 39: 347-356.

A Neuropsychological Approac h t o Intelligenc e · A Neuropsychological Approac h t o Intelligenc e ... NEUROPSI). No evident reason seems to exist to maintain this duality. It may

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