Imitation, Empathy, and Mirror Neuronssites.oxy.edu/clint/physio/article/imitationempathyandmirrorneurons.pdfImitation, Empathy, and Mirror Neurons Marco Iacoboni Ahmanson-Lovelace

ANRV364-PS60-25 ARI 24 November 2008 18:59

Imitation, Empathy,and Mirror NeuronsMarco IacoboniAhmanson-Lovelace Brain Mapping Center, Department of Psychiatry and BiobehavioralSciences, Semel Institute for Neuroscience and Social Behavior, Brain Research Institute,David Geffen School of Medicine at UCLA, Los Angeles, California 90095;email: [email protected]

Annu. Rev. Psychol. 2009. 60:653–70

First published online as a Review in Advance onSeptember 15, 2008

The Annual Review of Psychology is online atpsych.annualreviews.org

This article’s doi:10.1146/annurev.psych.60.110707.163604

Copyright c© 2009 by Annual Reviews.All rights reserved

0066-4308/09/0110-0653$20.00

Key Words

social cognition, theory of mind, mirror neuron system, embodiment

AbstractThere is a convergence between cognitive models of imitation, con-structs derived from social psychology studies on mimicry and empa-thy, and recent empirical findings from the neurosciences. The ideomo-tor framework of human actions assumes a common representationalformat for action and perception that facilitates imitation. Further-more, the associative sequence learning model of imitation proposesthat experience-based Hebbian learning forms links between sensoryprocessing of the actions of others and motor plans. Social psychol-ogy studies have demonstrated that imitation and mimicry are per-vasive, automatic, and facilitate empathy. Neuroscience investigationshave demonstrated physiological mechanisms of mirroring at single-celland neural-system levels that support the cognitive and social psychol-ogy constructs. Why were these neural mechanisms selected, and whatis their adaptive advantage? Neural mirroring solves the “problem ofother minds” (how we can access and understand the minds of others)and makes intersubjectivity possible, thus facilitating social behavior.

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Hebbian learning:associative learning isimplemented bysimultaneousactivation of cells thatwould lead toincreased synapticstrength between thecells

Contents

INTRODUCTION . . . . . . . . . . . . . . . . . . 654COGNITIVE MECHANISMS

OF IMITATION . . . . . . . . . . . . . . . . . . 654The Ideomotor Framework

of Imitation. . . . . . . . . . . . . . . . . . . . . 654Associative Sequence Learning . . . . . 656

IMITATION AND EMPATHYIN SOCIAL BEHAVIOR . . . . . . . . . . 657Pervasiveness and Automaticity

of Human Imitation. . . . . . . . . . . . . 657NEURAL MECHANISMS

OF IMITATION . . . . . . . . . . . . . . . . . . 659Neural Precursors

in Nonhuman Primates . . . . . . . . . 659Macaque Mirror Neurons

and Imitation in Monkeys . . . . . . . 662Human Brain Mechanisms

of Mirroring . . . . . . . . . . . . . . . . . . . . 663Neural Mirroring and Psychological

Theories of Imitation . . . . . . . . . . . 665WHY NEURAL MIRRORING

AND IMITATION? . . . . . . . . . . . . . . . 666

INTRODUCTION

Although mimicry is a pervasive phenomenonin the animal kingdom, imitation certainlyachieves its highest form in humans. Pastauthors—for instance, de Montaigne (1575),Adam Smith (1759), Poe (1982), Nietzsche(1881), and Wittgenstein (1980)—have oftenassociated imitation with the ability to em-pathize and understand other minds. The evo-lutionary, functional, and neural mechanismslinking imitation to empathy, however, havebeen unclear for many years. Recently, there hasbeen a convergence between cognitive mod-els of imitation, social psychology accounts ofits pervasiveness and its functional links withempathy and liking, and the neuroscience dis-coveries of neural mechanisms of imitationand empathy. This convergence creates a solidframework in which theory and empirical datareinforce each other.

Among cognitive models of imitation, theideomotor model and the associative sequencelearning model seem to map well onto neu-rophysiological mechanisms of imitation. Theideomotor model assumes a common rep-resentational format for action and percep-tion, whereas the associative sequence learningmodel puts at center stage Hebbian learning asa fundamental mechanism linking sensory rep-resentations of the actions of others to motorplans. Furthermore, social psychology studieshave documented the automaticity of imitationand mimicry in humans, a feature that also mapswell onto some recently disclosed neurophysi-ological bases of imitation.

This review discusses cognitive models, so-cial psychology constructs, and neural mech-anisms of imitation under the hypothesis thatthese mechanisms were selected because theyoffer the adaptive advantage of enabling the un-derstanding of the feelings and mental states ofothers, a cornerstone of social behavior.

COGNITIVE MECHANISMSOF IMITATION

The Ideomotor Frameworkof Imitation

Theories of action can be divided into twomain frameworks. The most dominant frame-work may be called the sensory-motor frame-work of action. It assumes that actions are ini-tiated in response to external stimuli. In thisframework, perception and action have inde-pendent representational formats. Stimuli mustbe translated into motor responses by stimulus-response mapping mechanisms. This frame-work has generated a large literature and el-egant experimental paradigms, as for instancethe work on stimulus-response compatibility(Hommel & Prinz 1997, Proctor & Reeve1990). Stimulus-response translational mecha-nisms, however, do not easily account for thesimilarity between the observed action and theaction performed by the imitator that is re-quired by imitation. Indeed, one of the mainproblems of imitation often discussed in the

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literature inspired by sensory-motor modelsis the so-called correspondence problem (Ne-haniv & Dautenhahn 2002). This problemcan be summarized with the question: how isthe sensory input from somebody else’s actiontransformed into a matching motor output bythe imitator?

For the ideomotor framework of action, thecorrespondence problem of imitation is not aproblem at all. Indeed, the ideomotor frame-work assumes a common representational for-mat for perception and action, an assump-tion that makes translational processes betweenstimuli and responses rather unnecessary. Theroots of the ideomotor framework were estab-lished by the work of Hermann Martin Lotze(Prinz 2005) and William James (1890). Thestarting point of actions, for Lotze and James,is not a response to a sensory stimulation, butrather the representation of the goal that theagent intends to achieve. When an intentionis unchallenged by a conflicting one, it acti-vates the representation of the intended goaland the motor plan necessary to achieve it. Thecoactivation of the intended goal and the mo-tor plan required to achieve it—according tothe ideomotor framework—is the result of ourexperience. We have learned the effects of ourown actions, and we expect certain effects whenwe perform certain acts. This previous learningmakes it possible that just thinking about theintended goal automatically activates the rep-resentation of the action necessary to obtain it.Thus, when I think about rebooting my com-puter, I automatically activate the representa-tion of the finger movement necessary to pressthe appropriate key.

The ideomotor framework naturally ac-counts for imitation. According to this frame-work, when I see somebody else’s actions andtheir consequences, I activate the representa-tions of my own actions that would producethose consequences. Here, consequences areconstrued in a very broad sense. For instance,a simple finger lifting has multiple perceptualconsequences, among them the sight of the fin-ger lifting. Thus, simply watching somebodyelse lifting a finger should activate my own mo-

tor plan to lift the same finger. Brass and col-leagues tested this hypothesis in elegantly sim-ple experiments (Brass et al. 2000, 2001). Sub-jects were shown two movements of the indexfinger from the same starting position. In halfof the trials the finger would move upward,and in the other half it would move downward.Subjects were instructed to respond as fast aspossible using their own index finger. Withineach block of trials, subjects were instructed touse always the same motor response, either anupward or a downward movement. Thus, al-though perceptually subjects were seeing bothupward and downward movements, motoricallythey were only executing one of the two move-ments. Given that response selection was notrequired, the identity of the stimulus was com-pletely irrelevant for the initiation of the motorresponse. Here, the sensory-motor frameworkwould predict similar reaction times for re-sponses that were identical to the stimulus (e.g.,upward motor response for a stimulus showingan upward finger movement) and for responsesthat were different from the stimulus (e.g., up-ward motor response for a stimulus showing adownward finger movement). In contrast, theideomotor framework would predict faster re-action times for motor responses identical tothe stimulus compared to motor responses dif-ferent from the stimulus. The results demon-strated a large chronometric advantage for re-sponses identical to the stimuli, in line with thepredictions of the ideomotor framework (Brasset al. 2000, 2001).

The ideomotor framework also predicts thatgoals have higher priority than movements inimitation. Imitation experiments in childrenhave confirmed this prediction. In one of theseexperiments (Bekkering et al. 2000), childrenand experimenters were sitting on the oppositesides of a desk. In half of the trials the experi-menter would place her or his left hand on theleft side of the desk (left ipsilateral movement)or on the right side of the desk (left contralateralmovement); in the remaining half of the trialsthe experimenter would place her or his righthand on the right side of the desk (right ipsilat-eral movement) or on the left side of the desk

www.annualreviews.org • Imitation, Empathy, and Mirror Neurons 655

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Associative sequencelearning: imitation isbased on associative,Hebbian-like learning,creating “verticallinks” between sensoryand motorrepresentations

(right contralateral movement). Children wereinstructed to “Do what I do,” and in all cases,they imitated all these movements well. In a sep-arate session, children and experimenters wereagain sitting on the opposite sides of the desk.Now, however, there were two big red dots, oneon the left and one on the right side of the desk.Whenever the experimenter made a movement,either ipsilateral or contralateral with either theleft or the right hand, the hand of the experi-menter would end up covering the big red dot.Children were again instructed to “Do what Ido.” In this situation, children imitated well theipsilateral movements but made frequent mis-takes when trying to imitate the contralateralmovements. Note that these movements hadbeen imitated well in absence of the big red dot.The presence of the big red dot had changed thegoal of the action to be imitated. Whereas inthe absence of the dot, the action itself was thegoal to be imitated, the presence of the dot hadchanged the goal of the action in covering thedot. Indeed, children made mistakes when im-itating contralateral movements because theyused ipsilateral movements to cover the samedot that had been covered by the experimenter.In other words, children would copy the goalbut used a simpler movement to achieve thisgoal (Bekkering et al. 2000).

One of the main assumptions of the ideo-motor framework is that action and perceptionshare a common representational format. Thisassumption fits well recent neuroscience dis-coveries, as discussed below. Another impor-tant assumption of the ideomotor frameworkis that our perceptual and motor experience isvery important in shaping the functional aspectsof imitation. This assumption is also shared bythe associative sequence learning model (Heyes2005), as described in the next section.

Associative Sequence Learning

The associative sequence learning model of im-itation proposes that imitative abilities are basedon associations between the sensory and mo-tor representation of actions. These associa-tions would be mostly shaped by experience,

although a small number of these associationsmay be innate. Several environmental situationsmay favor the establishment of these associ-ations between sensory and motor represen-tation of actions, for instance, visually guidedactions, such as reaching and grasping, duringwhich we can observe our own arm and handreach and grasp for objects surrounding us.Also, mirrors and other reflecting surfaces al-low the observation of one’s own facial and bodymovement as if they were performed by some-body else. Furthermore, early in human devel-opment, adults tend to imitate the baby (Nadel2002), thus favoring the formation of the asso-ciations between sensory and motor represen-tations of actions.

The basic assumption of the associativesequence learning model is that imitation isnot based on dedicated functional (and neural)mechanisms. General sensory and motor sys-tems may implement imitative abilities throughmechanisms that are strongly reminiscent ofHebbian learning. One of the corollaries of thisassumption is that imitation should not be con-fined to specific lineages. Indeed, although pri-mates clearly show varying degrees of imita-tive abilities, birds (Akins et al. 2002) and dol-phins (Herman 2002) also seem able to imi-tate. Thus, imitative behavior appears to be theproduct of convergent evolution. If this is true,then the hypothesis that imitation is mostlyshaped by experience—as assumed by the asso-ciative sequence learning model—is obviouslysupported.

The role of experience and the environmentin shaping imitative abilities may also accountfor evidence that at first sight seems at oddswith the basic assumptions of the associativesequence learning model. Many animals sharesimilar basic sensory and motor functional andneural mechanisms. In principle, this shouldlead to similar imitative skills in many ani-mals. Imitation abilities, however, vary substan-tially between species (Boysen & Himes 1999,Hurley & Chater 2005). Is this evidence a fa-tal blow to the main assumption of the asso-ciative sequence learning model? Probably not.Indeed, different kinds of environments may

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account for the differences in imitative abili-ties observed in different species. As discussedabove, some elements that are quite specific tothe human environment should favor the for-mation of the associations between sensory andmotor representations posited by the associa-tive sequence learning model. In keeping withthese ideas, humans are by far the best imitators(Hurley & Chater 2005).

Empirical evidence in well-controlled lab-oratory experiments seems to support the roleof experience in shaping imitation, as hypoth-esized by the associative sequence learningmodel. For instance, hand-opening and hand-closing gestures are typically facilitated by theobservation of the same movement compared tothe observation of a different movement. How-ever, this facilitation can be abolished by a rel-atively short period of training during whichsubjects are instructed to open the hand whileobserving hand closing, and to close the handwhile observing hand opening (Heyes et al.2005).

In another experiment, the effect of train-ing was measured on the speed of imitationinduced by the observation of human motionversus robotic motion. A typical finding is thathumans imitate more quickly the movements ofanother human compared to the movements ofa robot. This effect, however, may be simply be-cause humans tend to interact more with otherhumans than with robots. Indeed, subjects whowere trained to execute hand movement in re-sponse to a robotic movement demonstrated nodifference in speed of imitation while observ-ing human and robotic movements (Press et al.2007).

Although the associative sequence learningmodel and the ideomotor framework of imita-tion share the main idea that experience is ex-tremely important for imitation, they also seemto differ on an important point. The associativesequence learning model assumes that separatesensory and motor representations are linked byexperience. In contrast, the ideomotor frame-work assumes that sensory and motor func-tional mechanisms share a common represen-

tational format. In psychological terms, thesedifferences are not negligible. The translationof these different concepts into neural activity,however, as discussed below, may not differ dra-matically (Glimcher 2005). Indeed, the mainassumptions of both the associative sequencelearning model and the ideomotor frameworkof imitation fit well with recent neurosciencefindings on imitation.

IMITATION AND EMPATHYIN SOCIAL BEHAVIOR

Pervasiveness and Automaticityof Human Imitation

Humans seem to have a strong tendency to aligntheir behavior with their fellows during socialinteractions (Lieberman 2007). Some of theseforms of imitation and mimicry are not onlypervasive and automatic, but also operate ona quite complex level. Ap Dijksterius (2005)—following LeDoux’s terminology on processingof fearful stimuli (LeDoux 1996)—suggests thatthere are two roads to human imitation. A lowroad leads to imitation in a direct fashion, suchthat the perceiver acts the gestures, postures, fa-cial expressions, and speech perceived in otherpeople. A high road leads to complex and rathersubtle forms of imitation, as shown by a num-ber of experiments with priming manipula-tions that lead to stereotype activation or traitactivation.

An example of stereotype activation onmotor behavior is provided by the follow-ing experiment. Participants performed ascrambled-sentence language task. Some sub-jects were exposed to words such as Florida,bingo, gray; that is, words typically associatedwith the elderly. Some other subjects were not.After the experiment, participants left the labo-ratory and walked back to the elevator to leavethe building. An experimenter timed this walkback to the elevator. Subjects who had beenprimed with the elderly stereotype were reli-ably slower than subjects who had not beenprimed (Bargh et al. 1996). The primed subjects


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imitated—obviously in an unconscious way—the slowness of old people.

The high road to imitation is also at workin memory and general knowledge tasks. Inone experiment, subjects sat in front of a deskfull of objects. The stereotype of the elderlywas primed again in some subjects by askingthem questions on elderly people. Other sub-jects, in contrast, were asked questions aboutcollege students. Subsequently, subjects weretransferred to another room and were asked toremember the objects that were on the desk infront of them. The subjects primed with theelderly stereotype remembered far fewer ob-jects than did the other participants (Dijkster-huis et al. 2000).

In a series of experiments, participants wereeither asked to think about college professors(a group of people typically associated with in-telligence) and to write down everything thatcame to mind about college professors, or theywere asked to think about soccer hooligans(a group of people typically not associated withintelligence) and to write down everything thatcame to mind about soccer hooligans. In alater task involving general knowledge ques-tions, a task that was ostensibly unrelated tothe first one, the participants who were askedto think about college professors outperformedthe participants who were asked to think aboutsoccer hooligans. Indeed, the participants whowere asked to think about college professorseven outperformed participants who were notasked anything at all, and the participants whowere asked to think about soccer hooliganswere outperformed by participants who werenot asked anything at all (Dijksterhuis & vanKnippenberg 1998).

Many more studies support the concept thatthe high road to imitation is pervasive and auto-matic (Dijksterhuis 2005). The question is whypervasiveness and automaticity have been se-lected as distinctive properties of the high roadto imitation. One possibility is that imitation fa-cilitates social interactions, increases connect-edness and liking, gets people closer to eachother, and fosters mutual care. If this account

is correct, it should follow that good imita-tors should also be good at recognizing emo-tions in other people, which in turn may leadto greater empathy. Thus, this account wouldpredict a correlation between the tendency toimitate others and the ability to empathize withthem. This hypothesis was tested in a series ofexperiments (Chartrand & Bargh 1999). In thefirst experiment, subjects were asked to choosepictures in a set of photographs. The coverstory was that the researchers needed someof these pictures for a psychological test andwanted to know from the subjects which pic-tures they considered more stimulating. Whilesubjects were choosing the pictures, a confed-erate was sitting in the same room with the realsubject. The confederate pretended to be an-other subject who was also choosing good stim-ulating pictures. During the experimental ses-sions, some confederates deliberately rubbedtheir nose while the others shook their foot.Subjects were videotaped and their motor be-havior was measured. It was found that the realsubjects unintentionally mimicked the motorbehavior of the confederate with whom theywere sharing the room. Subjects who sharedthe room with confederates who rubbed theirnose, rubbed their nose more than did subjectswho shared the room with confederates whoshook their foot. Furthermore, subjects whoshared the room with confederates who shooktheir foot, shook their foot more than did sub-jects who shared the room with confederateswho rubbed their nose. These results are in linewith the idea that imitation is automatic andprovide the necessary prelude to the followingexperiments.

The second experiment tested the hypoth-esis that one of the functions of this automatictendency to imitate is to increase liking betweenindividuals. Participants were again asked tochoose pictures, and confederates were againsitting with them, pretending to be participantsof the study. In this second experiment, thecover task required participants and confeder-ates to take turns in describing what they sawin various photos. At the end of the interaction

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between participants and confederates, the par-ticipants were also asked to complete a ques-tionnaire to report how much they liked theother participant (that is, the confederate) andhow smoothly they thought the interaction hadgone. In this second experiment, the confeder-ates either imitated the spontaneous postures,movements, and mannerisms of the subjects orkept a neutral posture. The participants whowere mimicked by confederates during the in-teraction liked the confederates much morethan did the participants who were not im-itated. Furthermore, mimicked subjects ratedthe smoothness of the interaction higher thandid the participants who were not imitated.This experiment demonstrated that imitationand liking tend to go together. When some-one is imitating us, we tend to like him or hermore.

A third experiment tested the hypothesisthat the more people tend to imitate others, themore they are concerned with the feelings ofother people. The setting of this third experi-ment was identical to the first experiment. Thenovel aspect of this last experiment was that theparticipants responded to a questionnaire thatmeasured their empathic tendencies. The ex-periment found a strong correlation betweenthe tendency to empathize and the amount ofimitative behavior displayed by the participants.The more a subject imitated the confederate,the more that subject was an empathic individ-ual (Chartrand & Bargh 1999). This result sug-gests that through imitation and mimicry, weare able to feel what other people feel. By beingable to feel what other people feel, we are alsoable to respond compassionately to other peo-ple’s emotional states (Eisenberg 2000, Tangneyet al. 2007).

Many other empirical results are consis-tent with these ideas (Braten 2007, Niedenthalet al. 2005). What are the neural correlates ofthese complex forms of human behavior? A re-cent discovery in the monkey premotor cortexhas sparked a whole series of new studies, inmonkeys and humans, that are relevant to thisquestion.

Premotor cortex:anterior sector of theagranular frontalcortex containingneurons that arerelevant to theplanning, preparation,and selection of actions

Mirror neurons:neurons with motorproperties in premotorand posterior parietalcortex that fire notonly during actionexecution, but alsowhile observingsomebody elseperforming the sameor a similar action

NEURAL MECHANISMSOF IMITATION

Neural Precursorsin Nonhuman Primates

The premotor cortex of the macaque brain,a cortical region important for the plan-ning, preparation, and selection of movementsand coordinated actions, is not homogeneous(Matelli et al. 1985). It is composed of severalcito-architectonic fields with different physi-ological properties. In the lateral wall of themacaque brain, the ventral sector of the premo-tor cortex is composed of two main fields, areaF4 and area F5 (Matelli et al. 1985). Area F5 hasphysiological properties relevant to the neuralcontrol of mouth and hand movements, espe-cially grasping (Rizzolatti et al. 1988). Withinarea F5, there are neurons that discharge notonly when the monkey performs goal-orientedactions such as grasping an object, holding it,manipulating it, and bringing it to the mouth,but also when the monkey, completely still, sim-ply observes somebody else performing theseactions. Because of these properties, which al-most suggest that the monkey is observing itsown actions reflected by a mirror, these cellswere called mirror neurons (di Pellegrino et al.1992, Gallese et al. 1996).

The properties of mirror neurons call tomind the concepts of the ideomotor frame-work of actions, according to which perceptionand action share common representational for-mats. Indeed, mirror neurons embody the over-lap between perception and action predictedby the ideomotor framework by dischargingboth during action execution and during actionobservation.

The initial hypothesis about the functionalrole of mirror neurons focused on action recog-nition. By firing during actions of the self andof other individuals, mirror neurons may pro-vide a remarkably simple neural mechanism forrecognizing the actions of others. Early obser-vations on firing-rate changes in mirror neu-rons demonstrated that these cells do not fire atthe sight of a pantomime (Rizzolatti et al. 1996,


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Strictly congruentmirror neurons:mirror neurons thatfire during theobservation of exactlythe same action theycode motorically

Broadly congruentmirror neurons:mirror neurons thatfire during theobservation of anaction achieving thesame goal or logicallyrelated to the actionthey code motorically

Rizzolatti & Arbib 1998). For instance, the pan-tomime of whole-hand grasp (when the wholehand is used to grasp a relatively large object,as an orange) does not trigger the discharge ofa mirror neuron that fires during execution andobservation of whole-hand grasps. This makessense because monkeys typically do not pan-tomime. These early findings suggested that theproperties of this neural system were remark-able but relatively simple, some sort of “monkeysee, monkey do” neural mechanisms. However,many other findings contradict this view andrather suggest that mirror neurons form a so-phisticated, nuanced system for shared codingof motor and perceptual aspects of actions ofself and others (Rizzolatti & Craighero 2004).

For instance, although the term “mirror”implies a strong similarity between the executedand the observed actions, only one third ofmirror neurons—the so-called strictly congru-ent mirror neurons—fire for the same executedand observed action. The remaining two-thirdsof mirror neurons—the so-called broadly con-gruent mirror neurons—fire for executed andobserved actions that are not the same but ei-ther achieve the same goal or are logically re-lated (di Pellegrino et al. 1992, Gallese et al.1996, Rizzolatti & Craighero 2004), thus form-ing some sort of sequence of acts, as for instanceobserved placing food on the table and executedgrasping food and bringing it to the mouth.

The properties of broadly congruent mirrorneurons suggest that these cells provide a flex-ible coding of actions of self and others. Thisflexibility is an important property for success-ful social interactions because even though im-itation is a pervasive phenomenon in humans,people do not imitate each other all the timebut rather often perform coordinated, cooper-ative, complementary actions. Broadly congru-ent mirror neurons seem ideal cells to supportcooperative behavior among people (Newman-Norlund et al. 2007).

Following the initial observations (di Pelle-grino et al. 1992, Gallese et al. 1996), a seriesof more recent experiments have demonstratedother complex properties of mirror neurons.For instance, we often easily recognize actions

that are partially occluded. The role of mirrorneurons in the recognition of hidden actionswas tested by using a screen that occluded thecompletion of the grasping action (Umilta et al.2001). In two baseline conditions, the firing ofthe cells was measured for observation of grasp-ing and of grasp pantomime. As expected, mir-ror neurons fired for grasping observation butnot for observation of the pantomime. In a newexperimental condition, the subject watched agraspable object placed on a desk in front ofthe monkey. Subsequently, a screen occludedthe sight of the graspable object and a humanexperimenter reached with her or his hand be-hind the screen. The monkey was able to see theexperimenter’s hand moving toward the objectbut was not able to see the actual grasping ac-tion, which was occluded by the screen. Approx-imately half of the mirror neurons tested in thisexperiment discharged even though the grasp-ing action was occluded. The firing rate changesof these neurons were tested also in an addi-tional control condition. Here, at the beginningof the trial, the monkey saw that there was nograspable object on the table. As in the previousexperimental conditions, a screen subsequentlyoccluded the sight of the table and a human ex-perimenter reached with her or his hand behindthe screen. Consider that at this point, this ad-ditional control condition is visually identical tothe previous experimental conditions involvingthe screen occluding the sight of the graspingaction. The only difference here is the priorknowledge of the absence of a graspable objectbehind the screen. Mirror neurons tested un-der this experimental condition did not changetheir firing rate, suggesting that the unseen ac-tion behind the screen was indeed coded as apantomime (or, better, as a nongrasping action)(Umilta et al. 2001).

The experiment on hidden actions demon-strates another aspect of the properties ofmirror neurons that suggests that these cellscode actions in a fairly sophisticated way. Thesame visual information is coded differently,on the basis of prior knowledge about thepresence or absence of a graspable objectbehind the screen. A subsequent experiment

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demonstrated that mirror neurons also codein absence of any visual input (Kohler et al.2002). In this study, after the necessary baselineconditions were performed and mirror neuronswere identified, the experimenters measuredthe firing-rate changes of mirror neurons tothe sound of actions. The sound stimuli usedin this study were associated with commonactions such as tearing a piece of paper,breaking peanuts, and so on. Control soundsnot associated with actions, for instance whitenoise, were also used (Keysers et al. 2003,Kohler et al. 2002). The single-cell recordingsdemonstrated that mirror neurons can alsodischarge to the sound of an action, even inabsence of the visual input related to the action.These auditory properties of mirror neuronshave two important theoretical implications.One implication is relevant to the evolution oflanguage. Area F5 of the macaque brain (wheremirror neurons were originally discovered) isthe anatomical homologue of Brodmann area44 of the human brain (Rizzolatti & Arbib1998), a brain area with important languageproperties. This anatomical correspondence,together with other considerations, led tothe hypothesis that mirror neurons may havefacilitated the emergence of language inthe human brain (Rizzolatti & Arbib 1998).However, language is not only written andread but also (and mostly) spoken and heard.Mirror neuron responses to auditory stimuliare essential evidence for the hypothesis thatmirror neurons are important neural elementsin language evolution. The other implicationof the auditory properties of mirror neuronsis that they show that mirror neurons aremultimodal cells. This functional property istheoretically important because it is compatiblewith associative models of how mirror neuronsmay be formed, which is discussed in more de-tail below. When we break a peanut, the visualinput of our fingers breaking the peanut andthe auditory input of the sound of breaking thepeanut almost always co-occur, especially whenwe are initially learning to perform the action.Associative models can easily account formultimodal responses that are produced by the

co-occurrence of sensory stimuli from multiplemodalities (Fanselow & Poulos 2005, Keysers& Perrett 2004, Wasserman & Miller 1997).

A recent study on mirror neuron responsesto the sight of actions involving the use of toolsis also consistent with the hypothesis that theproperties of mirror neurons are shaped by ex-perience. Early observations on mirror neuronresponses to observed actions suggested thatthese cells do not fire at the sight of an ac-tion involving the use of a tool. For instance,a mirror neuron discharging during the execu-tion and observation of precision grips (whengrasping small objects with two fingers) wouldnot fire at the sight of the experimenter us-ing a hand tool such as a pliers to grasp thesame small object (Rizzolatti & Arbib 1998).However, a recent study recording in the infer-olateral aspect of area F5 has reported robustdischarges in approximately 20% of recordedmirror neurons when the monkey observed theexperimenters using tools (Ferrari et al. 2005).Indeed, these discharges were even more ro-bust than the discharges of the same cells dur-ing the observation of a grasping action with-out the tool (Ferrari et al. 2005). Although it isnot possible to demonstrate unequivocally thatthe mirror neuron responses to tool use actionswere acquired through the daily experience ofobserving human experimenters using tools inthe lab, this seems a likely explanation. It is un-likely that tool-use mirror neurons were alreadypresent in area F5 of the macaque brain butnever recorded for more than ten years. Thisrecently discovered functional property of mir-ror neurons and its likely underlying formingmechanisms is also obviously relevant to thepsychological theories discussed above.

Furthermore, described above, the ideomo-tor framework of action puts intentions frontand center. Is it possible that the discharge ofmirror neurons may represent the coding of theintention associated with the performed andobserved action rather than the action itself?A recent single-cell recording study has ad-dressed this question (Fogassi et al. 2005). Thedepth electrode recordings first demonstratedthat neurons in area PF/PFG—a cortical


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area located in the anterior part of the infe-rior parietal lobule that is anatomically con-nected with area F5 in the ventral premotorcortex (see Figure 1) and that also contains mir-ror neurons—had differential discharges for thesame grasping action that led to, say, eating foodrather than placing the food in a container (notethat the monkeys were rewarded after placingthe food in the container; thus, the amount ofreward was identical for both actions). Not sur-prisingly, grasping for eating was preferred bythe majority of grasping cells in this parietalarea, although approximately 25% of neuronscoding differently the same grasping action onthe basis of its intention preferred grasping forplacing over grasping for eating (Fogassi et al.2005).

This pattern of firing-rate changes demon-strates that these cells code the same executedgrasping action rather differently, according tothe intention (or the goal) associated with thegrasping action. The same pattern of firing-rate changes was also observed during actionobservation. Here, the monkey was simply ob-serving the human experimenter performinggrasping actions. The intention of the experi-menter was cued by the presence of a container.When the container was present, the experi-menter grasped the food and placed it in thecontainer. When the container was absent, theexperimenter grasped the food and ate it. At thetime of grasping, the cells that discharged morerobustly for grasping to eat when the monkeyperformed the actions also discharged more ro-bustly when the monkey simply observed thehuman experimenter grasping the food in or-der to eat it. Likewise, the cells that dischargedmore robustly for grasping to place when themonkey performed the actions also dischargedmore robustly when the monkey simply ob-served the human experimenter grasping thefood in order to place it in the container (Fo-gassi et al. 2005). Thus, rather than coding theobserved grasping action, these neurons seemto be coding the goal associated with the ac-tion, the intention to eat or to place.

The most dramatic demonstration of therole of goal coding in these cells has been pro-

vided by a very recent study (Umilta et al. 2008).Here, single-cell recordings in area F5 wereperformed after monkeys were trained to usepliers to grasp objects. Ventral premotor neu-rons active during grasping actions were alsoactive when the monkey used pliers to graspobjects. Monkeys were trained to use reversepliers that required hand opening rather thanhand closing (as in natural grasps). Remarkably,neurons that fired during hand closing in nat-ural grasps and during use of normal pliers didfire during hand opening when the monkeysused the reverse pliers. The activity of thesemotor neurons is evidently centered on cod-ing the goal of the action rather than the mo-tor detail of hand closing or opening. Amongthese motor neurons, the cells with mirroringproperties also demonstrated a pattern of firing-rate changes centered on goal coding, discharg-ing when the tips of the pliers were closing onthe objects to be grasped during observationof action with both normal and reverse pliers(Umilta et al. 2008).

Mirror neurons do not mirror only graspingactions performed with the hand or with toolscontrolled by the hand. There is evidence ofmirror neurons coding facial actions, in partic-ular with the mouth. Both ingestive (such as bit-ing and sucking) and communicative actions arecoded by mirror neurons (Ferrari et al. 2003).This is especially important for the hypothesisthat mirror neurons may facilitate our under-standing of the emotions of other people, be-cause the face is the body part that we use mostoften to express our own emotions.

Macaque Mirror Neuronsand Imitation in Monkeys

Do monkeys imitate? This is a contentious is-sue, and the answer to this question is heav-ily dependent on the definition of imitation.Among scholars, it was widely held at the endof the nineteenth century that monkeys notonly are able to imitate, but they actually doit “. . . at ludicrous length.” (Romanes 1883).In those times, imitation was not typically as-sociated with high forms of intelligence. This

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view of imitation has changed considerably inthe past 30 years (Hurley & Chater 2005), call-ing also for a revision of previously held ideason monkeys’ ability to imitate. Indeed, suchrevision had at some point taken the form ofa true backlash, with many scholars denyingthat monkeys had any imitative ability. Thisposition raised the issue of what is the adap-tive advantage of mirror neurons for monkeysand inspired new and better-controlled stud-ies. There is now well-controlled evidence thatmonkeys are indeed able to imitate (Ferrari et al.2006; Subiaul et al. 2004; Voelkl & Huber 2000,2007), and it is likely—although there is no di-rect evidence yet—that this ability is supportedby mirror neurons. For instance, marmosets ob-served a demonstrator removing the lids froma series of plastic canisters to obtain a meal-worm. Subsequently, marmosets that observeda demonstrator using its hands to remove thelids used only their hands, whereas marmosetsthat observed a demonstrator using its mouthused their mouth to remove the lids (Voelkl& Huber 2000). In another study, marmosetsobserved another marmoset (the model) thatwas previously trained to open a box in a pe-culiar way. Detailed motion analyses demon-strated that the highly unusual movement pat-tern of the model was faithfully replicated bythe observers (Voelkl & Huber 2007). A recentstudy has also shown that rhesus macaques dis-play neonatal imitation abilities that are simi-lar to the abilities displayed by human neonates(Ferrari et al. 2006).

It is evident, however, that imitative learningis not developed in monkeys as it is in humans(Hurley & Chater 2005). What then would bethe main function of mirror neurons in themonkey brain? One possibility might be thatmirror neurons facilitate the ability to recog-nize the actions of others. A recent behavioralstudy, however, has also revealed that monkeysare able to recognize when they are being imi-tated (Paukner et al. 2005). In this study, mon-keys observed two experimenters, each manip-ulating a wooden cube with a hole in each side.Initially, the monkeys did not show any prefer-ential looking between the two experimenters.

TMS: transcranialmagnetic stimulation

BOLD: blood-oxygenation-leveldependent

fMRI: functionalmagnetic resonanceimaging

Subsequently, a cube was given to the mon-key. When the monkey started manipulatingthe cube, one of the two experimenters imi-tated accurately the monkey’s actions directedat the cube. The second experimenter, in con-trast, performed different actions. At this point,the monkey preferentially looked at the exper-imenter imitating her own actions. This capac-ity, which is likely supported by mirror neu-rons, may have an important social function andmay be one of the early functional precursorsof the highly developed imitative behavior ofhumans.

Human Brain Mechanismsof Mirroring

The exquisite spatial and temporal resolu-tion afforded by depth electrode recordings ofsingle-cell activity can be obtained only withtechniques of brain investigation that are quiteinvasive. These techniques cannot typically beused in humans. The neural properties re-vealed by single-unit recordings in monkeys areusually investigated in humans at the systemlevel, with lesion studies (behavioral observa-tions on neurological patients), brain imaging,and recently transcranial magnetic stimulation(TMS). Although the relationships between allthese markers of brain activity are far from be-ing fully defined, there is evidence that theytend to correlate relatively well. Spiking neu-ronal activity recorded with in-depth electrodescorrelates well with the blood-oxygenation-level dependent (BOLD) signal measured byfunctional magnetic resonance imaging (fMRI)(Logothetis et al. 2001). In some cases, how-ever, spiking activity and BOLD seem to disso-ciate (Logothetis & Wandell 2004), for instancewhen spiking responses show adaptation (thatis, a reduced response to repeated stimuli) whileBOLD does not (Goense & Logothetis 2008).Nevertheless, a recent TMS study has shownsimilar stimulation effects on both neural andhemodynamic signals (Allen et al. 2007), sup-porting the practice of inferring neural activityfrom signals based on hemodynamic changes,such as BOLD fMRI.


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Pars opercularis:posterior sector of theinferior frontal gyrusdelimited superiorlyby the inferior frontalsulcus, inferiorly bythe Sylvian fissure,posteriorly by theventral sector of theprecentral gyrus, andanteriorly by theascending branch ofthe Sylvian fissure.Pars opercularis in theleft hemisphere isclassically consideredthe posterior part ofBroca’s area, a majorlanguage area of thehuman brain

Indeed, this practice is widely used in sys-tems neuroscience. For instance, single-cellrecordings with depth electrodes have revealedin the dorsal premotor cortex of macaques cel-lular mechanisms of conditional motor learn-ing, the fundamental ability that allows theassociation of motor responses to arbitrary sen-sory stimuli, as when we brake at a red trafficlight. In humans, the dorsal premotor cortexhas also been associated with conditional mo-tor learning by brain imaging and lesion stud-ies (Passingham 1993). Even though single-cellrecordings of human dorsal premotor neuronshave not been performed, the obvious assump-tion is that the human brain must have dor-sal premotor cellular mechanisms that enableconditional motor learning and that are likelysimilar to—albeit probably more sophisticatedthan—the ones recorded in monkeys.

This very same logic applies to the investi-gation of mirror neurons in the human brain.Given that the information typically obtained inhuman studies is at system level, the term “mir-ror neuron system” is often used in these stud-ies. Two positron emission tomography studies(Grafton et al. 1996, Rizzolatti et al. 1996) anda TMS study (Fadiga et al. 1995) provided earlyevidence compatible with the idea that the hu-man ventral premotor and inferior frontal cor-tex had mirroring properties. However, thesestudies did not investigate the role of these hu-man brain areas in imitation. In a later fMRIstudy (Iacoboni et al. 1999), subjects were re-quired to imitate simple finger movements andto perform motor and visual control tasks. Thelogic of the study was as follows: The neuronaldischarge measured by depth electrode record-ings in macaques during action observation isapproximately 50% of the discharge measuredduring action execution (Gallese et al. 1996).Thus, human brain areas with mirror neuronsshould also have an increased BOLD signal(which roughly correlates with brain activity infMRI) during action observation that is approx-imately 50% of the BOLD increase measuredduring action execution. Furthermore, duringimitation, subjects were simultaneously watch-

ing the finger movement and copying it. Thus,mirror neuron areas may have a BOLD sig-nal increase during imitation that is approxi-mately the sum of the BOLD signal increasesobserved during action observation and dur-ing action execution. The fMRI study foundthat two cortical areas had this predicted pat-tern of activity: They were located in the pos-terior part of the inferior frontal gyrus and inthe rostral part of the posterior parietal cor-tex (Iacoboni et al. 1999), in anatomical loca-tions (Figure 2) that were homologous to theanatomical locations of the macaque brain ar-eas with mirror neurons, that is, area F5 inthe ventral premotor cortex and area PF/PFGin the rostral sector of the inferior parietallobule.

The inferior frontal area with mirroringproperties overlapped with the posterior partof Broca’s area, a major language area. On onehand, these findings supported the evolution-ary hypothesis about the role of mirror neu-rons in language (Rizzolatti & Arbib 1998).On the other hand, an activation in a languagearea during a nonlanguage task may be in-duced by covert verbalization occurring duringthe activation tasks. It is unclear why imitationshould induce more covert verbalization thanmotor execution, which in turn should inducemore covert verbalization than action observa-tion (the pattern predicted for a mirror neuronarea and observed in the posterior part of theinferior frontal gyrus and in the rostral part ofthe posterior parietal cortex), and this issue can-not be conclusively resolved by fMRI, which is atechnique that provides only correlational databetween brain areas and human behavior. TMS,on the other hand, provides information on thecausal role of the activity in a brain area andhuman behavior. A high-frequency repetitiveTMS study indeed demonstrated later that ac-tivity in the pars opercularis, the posterior partof the inferior frontal gyrus, is essential to imi-tation (Heiser et al. 2003).

A series of brain-imaging studies has sug-gested a core cortical circuitry for imitationcomposed of the posterior part of the superior

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temporal sulcus, a higher-order visual area thatresponds to watching biological motion andintentional actions (Allison et al. 2000, Jellemaet al. 2000, Perrett et al. 1989, Puce & Perrett2003, Puce et al. 1998), and by the parietaland frontal mirror neuron areas. Within thiscortical circuitry, the superior temporal cortexwould provide a higher-order visual descriptionof the actions of other people and would feedthis information to the fronto-parietal mirrorneuron areas (Iacoboni et al. 2001). The pari-etal mirror neuron area would code the mo-tor aspect of the action (Iacoboni et al. 1999),whereas the frontal mirror neuron area wouldbe more concerned with the goal of the action(Iacoboni 2005, Iacoboni et al. 2005, Iacoboni& Dapretto 2006, Koski et al. 2002).

Imitative behavior can take many forms(Hurley & Chater 2005). The core circuitry forimitation, composed of superior temporal cor-tex, inferior parietal lobule, and inferior frontalcortex, interacts with other neural systems tosupport different forms of imitative behavior.For instance, the interactions between the corecircuitry for imitation and the dorsolateral pre-frontal cortex seem critical during imitativelearning (Buccino et al. 2004). In contrast, so-cial mirroring and the ability to empathize withothers may be supported by the interactions be-tween the core circuitry for imitation and thelimbic system (Iacoboni 2005). An fMRI studyof imitation and observation of facial emotionalexpressions (Carr et al. 2003) tested the hypoth-esis that empathy is enabled by a large-scaleneural network composed of the mirror neu-ron system, the limbic system, and the insulaconnecting these two neural systems. Withinthis network, mirror neurons would support thesimulation of the facial expressions observed inother people, which in turn would trigger ac-tivity in limbic areas, thus producing in the ob-server the emotion that other people are feeling.This model predicts activation of mirror neu-ron areas, insula, and limbic areas during bothobservation and imitation of facial emotionalexpressions. Furthermore, the model predictsthat the increased activity in mirror neuron ar-

eas during imitation should also spread to insulaand limbic areas, if these brain centers are in-deed functionally connected with mirror neu-ron areas. Both predictions were supported bythe empirical findings (Carr et al. 2003).

In functional terms, the large-scale net-work composed of mirror neuron areas, in-sula, and the limbic system likely provides asimulation-based form of empathy (Goldman2006, Goldman & Sripada 2005). Recent dataalso suggest that the activity in this networkprovides a biomarker of sociality and empa-thy. Indeed, an fMRI study of imitation andobservation of facial expressions in childrenwith autism and in typically developing chil-dren demonstrated not only a deficit in mir-ror neuron areas in the children with autism,but also a correlation between the severity ofthe disease and activity in these areas: Thelower the activity in mirror neuron areas, themore severe the autism (Dapretto et al. 2006).Furthermore, a separate fMRI study on typi-cally developing preadolescents—in which theactivation task was again the observation andimitation of facial emotional expressions—hasrecently demonstrated that activity in mirrorneuron areas was positively correlated with in-terpersonal competence and empathic concern(Pfeifer et al. 2008). Two additional fMRI stud-ies on adults also support the findings obtainedin children. In one study, subjects observed sim-ple grasping actions (Kaplan & Iacoboni 2006).In the other study, subjects listened to actionsounds (Gazzola et al. 2006). Both studies founda positive correlation between empathy scoresand activity in premotor areas activated dur-ing action observation and while listening toaction sounds, thus likely containing mirrorneurons.

Neural Mirroring and PsychologicalTheories of Imitation

The ideomotor model of imitation and theassociative sequence learning model sharemany concepts but diverge on a fundamen-tal one: The former assumes overlap between


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perceptual and motor representations, whereasthe latter assumes that sensory and motorrepresentations are separated but functionallyconnected through vertical links formed by as-sociative learning. Both models also map wellonto the functional properties of mirror neu-rons and neural systems for mirroring. Do theneuroscience findings on mirror neurons bet-ter support the assumptions of the ideomotormodel on perceptual and motor representationsor those of the associative sequence learningmodel? It is difficult to answer this questionbecause the levels of description of psychologi-cal theories and those of neuroscience empiricalwork are radically different.

The discharge of mirror neurons during ac-tion execution and action observation seemsto fulfill the main assumption of the ideo-motor model, a common representational for-mat for perception and action. Preliminary re-sults on individual neuronal activity obtainedwith depth electrode recordings in humans (R.Mukamel, A. Ekstrom, J. Kaplan, M. Iacoboniand I. Fried, unpublished observations) seemalso to support the ideomotor model. Using arare clinical opportunity, we recently recordedsingle-cell activity in epileptic patients im-planted for surgical evaluation. We found hu-man neurons with mirror properties in thefrontal lobe as well as in the medial temporalcortex. Although the discharge of these cellsduring action execution and action observationseems to imply a common representational for-mat for perception and action implemented atsingle cell level, it is also true that lesions inthe frontal lobe are more often associated withmotor deficits, and lesions in the medial tem-poral lobe are more often associated with per-ceptual deficits. Perception and action, whichare united at the level of single cells, seem tobe more easily separated at the system level.In principle, the discharge during action exe-cution and during action observation of frontaland medial temporal neurons may represent inneural terms the “vertical links” posited by theassociative sequence learning model between asensory unit (the medial temporal neuron) and

a motor unit (the frontal neuron) that fire to-gether as a result of associative learning.

WHY NEURAL MIRRORINGAND IMITATION?

The fundamental Darwinian question is whymirror neurons were selected by evolution.What is the adaptive advantage of having theseneurons? The properties of these cells seem tosolve—or better, dis-solve—what is called the“problem of other minds”: if one has access onlyto one’s own mind, how can one possibly un-derstand the minds of other people? How canone possibly share one’s own mental states withothers, making intersubjectivity possible?

A classical solution to the problem of otherminds is the so-called argument from analogy.The argument from analogy posits that we firstobserve certain relations between our mentalstates and our bodily states and then find ananalogy between our body and the body of otherpeople. If there is an analogy between our bodyand the body of others, there may be also ananalogy between our mental states/bodily statesrelations and those of other people. This wayof reasoning about the mental states of otherpeople seems too complex for something weseem to accomplish so naturally, effortlessly,and quickly. Mirror neurons, in contrast, pro-vide a prereflective, automatic mechanism ofmirroring what is going on in the brain ofother people that seems more compatible withour ability to understand others effortlessly andwith our tendency to imitate others automati-cally, as we have discussed in this review.

A further implication of the recent work onthe relationships between mirror neurons, im-itation, and empathy is the consideration thatthe evolutionary process made us wired forempathy. This is a major revision of widelyheld beliefs. Traditionally, our biology is con-sidered the basis of self-serving individualism,whereas our ideas and our social codes enableus to rise above our neurobiological makeup.The research on mirror neurons, imitation,and empathy, in contrast, tells us that our

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ability to empathize, a building block of our so-ciality (Adolphs 2009) and morality (de Waal2008, Tangney et al. 2007), has been built “bot-

tom up” from relatively simple mechanismsof action production and perception (Iacoboni2008).

SUMMARY POINTS

1. Imitation is pervasive and automatic in humans.

2. Psychological models of imitation that assume an overlap or strong associative linksbetween perception and action are supported by neural mirroring.

3. The core neural circuitry of imitation is composed of a higher-order visual area (theposterior part of the superior temporal sulcus) and by the fronto-parietal mirror neuronsystem.

4. Empathy is implemented by a simulation of the mental states of other people.

5. A large-scale network for empathy is composed of the mirror neuron system, the insula,and the limbic system.

6. Mirror neurons were selected because they provide the adaptive advantage of intersub-jectivity.

FUTURE ISSUES

1. What are the anatomical locations and physiological properties of mirror neurons inhumans? Depth electrode recordings in neurological patients may be able to investigatethis issue.

2. How can we more precisely map the predictions of psychological models onto empiricalfindings from the neurosciences?

3. What are the developmental mechanisms that shape the mirror neuron system?

4. What are the factors that influence the ability to empathize with other people?

DISCLOSURE STATEMENT

The author is not aware of any biases that might be perceived as affecting the objectivity of thisreview.

ACKNOWLEDGMENTS

For generous support, I thank the Brain Mapping Medical Research Organization, Brain MappingSupport Foundation, Pierson-Lovelace Foundation, The Ahmanson Foundation, William M.and Linda R. Dietel Philanthropic Fund at the Northern Piedmont Community Foundation,Tamkin Foundation, Jennifer Jones-Simon Foundation, Capital Group Companies CharitableFoundation, Robson Family, and Northstar Fund.

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Describes mirrorneurons responding tohidden actions.

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www.annualreviews.org ● Imitation, Empathy, and Mirror Neurons C-1

Figure 1

Schematic drawing of the lateral wall of the macaque brain. The inferior frontal (ventral premotor area F5)and inferior parietal (PF and PFG) areas circled in red contain mirror neurons. (Modified from figure 1 ofRizzolatti & Craighero 2004.)

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C-2 Iacoboni

Figure 2

Lateral wall of the human brain. Human areas presumed to contain mirror neurons are in the posteriorpart of the inferior frontal gyrus and in the anterior part of the inferior parietal lobule.

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AR364-FM ARI 11 November 2008 15:42

Annual Review ofPsychology

Volume 60, 2009Contents

Prefatory

Emotion Theory and Research: Highlights, Unanswered Questions,and Emerging IssuesCarroll E. Izard � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 1

Concepts and Categories

Concepts and Categories: A Cognitive Neuropsychological PerspectiveBradford Z. Mahon and Alfonso Caramazza � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �27

Judgment and Decision Making

Mindful Judgment and Decision MakingElke U. Weber and Eric J. Johnson � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �53

Comparative Psychology

Comparative Social CognitionNathan J. Emery and Nicola S. Clayton � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �87

Development: Learning, Cognition, and Perception

Learning from Others: Children’s Construction of ConceptsSusan A. Gelman � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 115

Early and Middle Childhood

Social Withdrawal in ChildhoodKenneth H. Rubin, Robert J. Coplan, and Julie C. Bowker � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 141

Adulthood and Aging

The Adaptive Brain: Aging and Neurocognitive ScaffoldingDenise C. Park and Patricia Reuter-Lorenz � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 173

Substance Abuse Disorders

A Tale of Two Systems: Co-Occurring Mental Health and SubstanceAbuse Disorders Treatment for AdolescentsElizabeth H. Hawkins � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 197

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Therapy for Specific Problems

Therapy for Specific Problems: Youth Tobacco CessationSusan J. Curry, Robin J. Mermelstein, and Amy K. Sporer � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 229

Adult Clinical Neuropsychology

Neuropsychological Assessment of DementiaDavid P. Salmon and Mark W. Bondi � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 257

Child Clinical Neuropsychology

Relations Among Speech, Language, and Reading DisordersBruce F. Pennington and Dorothy V.M. Bishop � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 283

Attitude Structure

Political Ideology: Its Structure, Functions, and Elective AffinitiesJohn T. Jost, Christopher M. Federico, and Jaime L. Napier � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 307

Intergroup relations, stigma, stereotyping, prejudice, discrimination

Prejudice Reduction: What Works? A Review and Assessmentof Research and PracticeElizabeth Levy Paluck and Donald P. Green � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 339

Cultural Influences

Personality: The Universal and the Culturally SpecificSteven J. Heine and Emma E. Buchtel � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 369

Community Psychology

Community Psychology: Individuals and Interventions in CommunityContextEdison J. Trickett � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 395

Leadership

Leadership: Current Theories, Research, and Future DirectionsBruce J. Avolio, Fred O. Walumbwa, and Todd J. Weber � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 421

Training and Development

Benefits of Training and Development for Individuals and Teams,Organizations, and SocietyHerman Aguinis and Kurt Kraiger � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 451

Marketing and Consumer Behavior

Conceptual ConsumptionDan Ariely and Michael I. Norton � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 475

viii Contents

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Psychobiological Mechanisms

Health Psychology: Developing Biologically Plausible Models Linkingthe Social World and Physical HealthGregory E. Miller, Edith Chen, and Steve Cole � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 501

Health and Social Systems

The Case for Cultural Competency in Psychotherapeutic InterventionsStanley Sue, Nolan Zane, Gordon C. Nagayama Hall, and Lauren K. Berger � � � � � � � � � � 525

Research Methodology

Missing Data Analysis: Making It Work in the Real WorldJohn W. Graham � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 549

Psychometrics: Analysis of Latent Variables and Hypothetical Constructs

Latent Variable Modeling of Differences and Changes withLongitudinal DataJohn J. McArdle � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 577

Evaluation

The Renaissance of Field Experimentation in Evaluating InterventionsWilliam R. Shadish and Thomas D. Cook � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 607

Timely Topics

Adolescent Romantic RelationshipsW. Andrew Collins, Deborah P. Welsh, and Wyndol Furman � � � � � � � � � � � � � � � � � � � � � � � � � � � � 631

Imitation, Empathy, and Mirror NeuronsMarco Iacoboni � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 653

Predicting Workplace Aggression and ViolenceJulian Barling, Kathryne E. Dupre, and E. Kevin Kelloway � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 671

The Social Brain: Neural Basis of Social KnowledgeRalph Adolphs � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 693

Workplace Victimization: Aggression from the Target’s PerspectiveKarl Aquino and Stefan Thau � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 717

Indexes

Cumulative Index of Contributing Authors, Volumes 50–60 � � � � � � � � � � � � � � � � � � � � � � � � � � � 743

Cumulative Index of Chapter Titles, Volumes 50–60 � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 748

Errata

An online log of corrections to Annual Review of Psychology articles may be found athttp://psych.annualreviews.org/errata.shtml

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Imitation, Empathy, and Mirror Neuronssites.oxy.edu/clint/physio/article/imitationempathyandmirrorneurons.pdfImitation, Empathy, and Mirror Neurons Marco Iacoboni Ahmanson-Lovelace

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