New Insights into Insight: Neurophysiological Correlates ... · This paper will close this gap by examining the differences between the intrinsic “aha” and ... instance, the following

Preprint submitted to Neuropsychologia December 8, 2016

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New Insights into Insight: Neurophysiological Correlates of the Difference

Between the Intrinsic “Aha” and the Extrinsic “Oh Yes” Moment

Katrin Rothmalera,*, Roland Nigburb, Galina Ivanovac,d,e a Department of Computer Sciences, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany.

b Department of Psychology, Otto-von-Guericke-University Magdeburg, Postfach 4120, 39106 Magdeburg, Germany. c Department of Psychology, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany.

d Institute for Applied Informatics at Leipzig University, Hainstraße 11, 04109 Leipzig, Germany. e Information Systems Institute, Leipzig University, Grimmaische Straße 12, 04109 Leipzig, Germany.

___________________________________________________________________________

Abstract

Insight refers to a situation in which a problem solver immediately changes his understanding

of a problem situation. This representational change can either be triggered by external

stimuli, like a hint or the solution itself, or by internal solution attempts. In the present paper,

the differences and similarities between these two phenomena, namely “extrinsic” and

“intrinsic” insight, are examined. To this end, electroencephalogram (EEG) is recorded while

subjects either recognize or generate solutions to German verbal compound remote associate

problems (CRA). Based on previous studies, we compare the alpha power prior to insightful

solution recognition with the alpha power prior to insightful solution generation. Results

show that intrinsic insights are preceded by an increase in alpha power at right parietal

electrodes, while extrinsic insights are preceded by a respective decrease. These results can

be interpreted in two ways. In consistency with other studies, the increase in alpha power

before intrinsic insights can be interpreted as an increased internal focus of attention.

Accordingly, the decrease in alpha power before extrinsic insights may be associated with a

more externally oriented focus of attention. Alternatively, the increase in alpha power prior to

intrinsic insights can be interpreted as an active inhibition of solution-related information,

while the alpha power decrease prior to extrinsic insights may reflect its activation.

Regardless of the interpretation, the results provide strong evidence that extrinsic and

intrinsic insight differ on the behavioral as well as the neurophysiological level.

Keywords: problem solving; solution recognition; EEG; alpha power; right hemisphere; insight

___________________________________________________________________________

*Corresponding author, email: [email protected]

Preprint originally published in Neuropsychologia, ELSEVIER, Vol 95, Jan 2017, pp 204-2014, doi: 10.1016/j.neuropsychologia.2016.12.17

Rothmaler et al.: New Insights Into Insight

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1 Introduction

Throughout history, some of the most important scientific achievements were accomplished

by a sudden flash of inspiration that instantly changed the discoverer’s understanding of the

problem situation. The discovery of Archimedes’ principle is a popular example of such an

insight experience. According to the anecdote, Archimedes of Syracuse was asked to develop

a non-destructive testing method for the royal crown. After a few unsuccessful attempts, he

finally found the solution while taking a bath. Various storytellers claim that Archimedes got

in the tub and saw the water level rise, which immediately triggered the answer to his

problem. However, it is also possible that taking the bath was simply relaxing him, enabling

his mind to draw connections where he never expected them. Unfortunately, we cannot ask

Archimedes whether the rising water level or the total relaxation elicited his “aha” moment.

Nevertheless, we can raise the question if it would have made any difference. We can even

go one step further and ask: would it have been the same if someone had told Archimedes the

solution?

The central question of the present study is whether there is any difference between an active

insightful solution generation, referred to as intrinsic insight, and a more passive solution

recognition, referred to as extrinsic insight. According to Wertheimer (1945), extrinsic

insight is unlikely to produce the restructuring necessary for real insightful understanding.

Thereby, restructuring designates “the process of arriving at a new understanding of the

problem situation” (Dominowski and Dallob, 1995, p. 50). Behavioral studies support

Wertheimer’s hypothesis by showing that participants who find solutions to insight problems

on their own exhibit a far better recall rate than subjects confronted with the correct solution

after failing to solve a problem (cf. Dominowski and Buyer, 2000). In addition, Metuki et al.

(2012) demonstrate that transcranial direct current stimulation (tDCS) over the left

dorsolateral prefrontal cortex significantly improves solution recognition of difficult verbal

insight problems but not their solution generation. Electrophysiological evidence reviewed by

Dietrich and Kanso (2010) suggests that even two opposing ERP results can be traced back to

a confusion of intrinsic and extrinsic insight: While intrinsic insight is associated with a

positive event-related potential after stimulus onset (P200-600) over the superior temporal

gyrus (Qiu et al., 2008), extrinsic insight is related to a negative one (N320) (Qiu et al.,

2006). These results already indicate that extrinsic and intrinsic insight differ on the

behavioral as well as the neurophysiological level. Nevertheless, various neuroscientific


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insight studies assume that the presentation of a solution or a solution hint results in the same

“aha” moment as an internally generated solution attempt (cf. Luo et al., 2004; Luo and Niki,

2003; Mai et al., 2004; Qiu et al., 2006; Shen et al., 2013). Although several authors already

questioned this assumption (for reviews, Bowden et al., 2005; Kounios and Beeman, 2014;

Luo and Knoblich, 2007), so far no neuroscientific study has investigated this essential issue.

This paper will close this gap by examining the differences between the intrinsic “aha” and

the extrinsic “oh yes” moment on a neurophysiological level.

1.1 Operationalization of Insight

One definition of insight is given by Dominowski and Dallob (1995, p. 33) who describe it as

a “form of understanding (of a problem and its solution) that can result from restructuring, a

change in a person’s perception of a problem situation”. This definition covers both: the

active insightful solution generation and the more passive insightful solution recognition. In

the following, the former will be called intrinsic insight, while the latter will be referred to as

extrinsic insight. Another way to define insight is to distinguish it from alternative problem

solving strategies. Typically, one contrasts insight and analysis. Analytic problem solving is

characterized by a methodological and strategic processing towards the solution (cf. Wegbreit

et al., 2012). Analytic problem solvers gradually approach the solution and are well aware of

their solution path (cf. Metcalfe and Wiebe, 1987). In contrast, insightful solutions arise

suddenly and unpredictably (cf. Metcalfe and Wiebe, 1987), they often involve a mental

impasse (cf. Duncker, 1945) and the inability to report the processing that led to the solution

(cf. Maier, 1931; Schooler et al., 1993).

For several years, it was common practice to use two distinct classes of tasks to study

insightful and analytic problem solving: insight and non-insight (or analytic) problems (cf.

Dominowski and Dallob, 1995). A popular example of an insight problem is Duncker’s

candle-box-task. The task is to attach three candles side by side at eye level on a door. To do

so, the problem solver has three small pasteboard boxes containing small candles, tacks and

matches, respectively. The solution consists of emptying the boxes and tacking them to the

door so that they can be used as a platform for the candles (Duncker, 1945). On the other

hand, the Wason selection task is a famous example of an analytic problem. This task

consists of four cards, each of which has a letter on one side and a number on the other. The

problem solver sees just one side of the cards. These visible faces show „A“, „B“, „4“ and

„7“. He has to decide which cards he needs to turn to check the following rule: If a card has


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an „A“ on one side, then it must have a „4“ on the other side. The solution is to turn the card

showing “A” and the card showing “4” (Wason, 1966).

With the use of two mutually exclusive classes of problems, it was implicitly assumed that

problems of a particular class can only be solved with the associated problem solving

strategy. However, this assumption does not hold true for all insight problems. Consider, for

instance, the following brain-teaser: “If you have black socks and brown socks in a drawer,

mixed in a ratio of 4 to 5, how many socks will you have to take out to make sure that you

have a pair of the same color?“ (Bowden et al., 2005, p. 323). Bowden et al. (2005) argue that

this insight problem can also be solved with a “What if”-strategy: “What if I take out a black

sock then a brown sock? I would only need one more sock of either color to have a pair of the

same color.“ (Bowden et al., 2005, p. 323). This observation led to a new experimental

paradigm: instead of seeking exclusive insight problems, Bowden and Jung-Beeman

deliberately utilized tasks that could be solved by either insight or analysis (1998). To

separate solutions with and without insight, they used the subjective experience of their

participants. Thus, subjects were asked to rate on a trial-by-trial basis whether they achieved

their answer via insight or analysis (cf. Bowden, 1997). This insight judgment procedure has

been successfully applied in various following studies (for review, Kounios and Beeman,

2014) and it is especially valuable for neuroimaging studies that require an adequate

reference state for analysis (for reviews, Bowden et al., 2005; Kounios and Beeman, 2009).

Contrary to the scientific consensus regarding solution generation, there is still an ongoing

debate whether solution recognition can either be achieved via insight or analysis. While

some researchers doubt the existence of an insightful solution understanding (cf. Wertheimer,

1945), others deny the existence of its analytic comprehension (cf. Luo and Niki, 2003; Mai

et al., 2004; Qiu et al., 2006; Shen et al., 2013). However, Bowden and Jung-Beeman (2003a)

successfully demonstrated that subjects can recognize solutions with and without “aha”

moment. Therefore, we will use the subjective ratings of the participants in the present study

to distinguish these different kinds of understanding.

1.2 State of the Art and Hypotheses

As mentioned previously, intrinsic insight involves restructuring, a change in the initial

problem representation. This definition implies that the initial understanding of the problem

situation is invalid, probably misdirected by past experiences, context or familiarity (cf.


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Dominowski and Dallob, 1995). To solve a problem via insight, the problem solver needs to

think outside the box and establish new and innovative associative or semantic relations

(Jung-Beeman et al., 2004). In their neurological model of intrinsic insight, Bowden and

colleagues (2005) suggest that the initial processing of a problem already activates these

remote associations. Yet, this activation is weak and remains unconscious. The behavioral

experiment of Bowden (1997) provides evidence for such an unconscious pre-activation of

solution-related information in connection with intrinsic insight. In his study, participants

were asked to solve a series of anagrams. Prior to some anagrams, either the solution, a

semantically related or an unrelated word was presented. This prior hint was presented either

too brief to be detected, too brief to be identified (i.e. unreportable) or long enough to be

reported. After each solution, the subjects rated their subjective experience of insight on a 10-

point scale. Since these insight ratings are not interpretable for reportable hints, they were

excluded from the analysis. For undetectable hints, all hints lead to reliably higher ratings of

insight than without hint presentation. Thereby, no differences between the hint types can be

observed. The authors conclude that the mere presentation of a stimulus (even if it is

completely uninformative) attracts attention and elicits a preparedness response that

manifests itself in the subjects’ insight ratings. In contrast, a reliable effect of hint type on

insight rating is found for unreportable hints. As expected, the presentation of a hint results in

significantly higher insight ratings than without hint presentation. Furthermore, solution hints

lead to marginally higher insight ratings than semantically related hints, which, in turn, lead

to significantly higher ratings than unrelated hints. These results indicate that the

unreportable processing of solution-related concepts is crucial for insight experiences.

Moreover, the unconscious processing of information seems to be associated with insight

experiences even if the information is completely unrelated to the solution.

Bowden and colleagues (2005) further localize the weak activation of solution-related

information within the right hemisphere. This hypothesis is supported by the work of Fiore

and Schooler (1998) who demonstrate that hints to classical insight problems are more

valuable when presented to the left visual hemifield than to the right hemifield. In addition,

Bowden and Jung-Beeman (1998) reveal a connection between solution priming, solution

recognition and the right hemisphere. They use semantic association problems that demand a

single word as their solution and give the participants 15s to solve them. Afterwards, a

lateralized target word is presented that is either the correct solution or a completely

unrelated word. Subjects are asked to name the target word or to decide if it represents the


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correct solution. Participants name solution words faster than unrelated words. This solution

priming is greater for solutions that are presented to the left visual field than for solutions that

appear in the right hemifield. If subjects fail to solve the problem, the solution priming is

even limited to the left visual field. In addition, participants recognize solutions to unsolved

problems faster if they are presented at the left visual hemifield. These results are consistent

with previous findings that associate the right hemisphere with a coarse semantic coding (cf.

Beeman, 1993; Chiarello et al., 1990). This coarse semantic coding produces large and weak

semantic fields comprising a variety of information including concepts that are only distantly

related to the input word and context (cf. Beeman, 1993), which makes it especially

important for insight solutions (cf. Jung-Beeman et al., 2004).

According to Bowden and colleagues (2005) the weak activation of non-obvious but

solution-relevant information in the right hemisphere is overshadowed by the strong

activation of obvious, problem-related concepts that do not lead to a solution. To solve the

problem, the solver needs to “switch the focus of processing to the unconscious activation”

(Bowden et al., 2005, p. 324). Hence, insightful problem solving is associated with an

increased internal focus of attention (cf. Jung-Beeman et al., 2004; Salvi et al., 2015). With

their eye movement study, Salvi et al. (2015) provide direct evidence for such a connection

between internally oriented attention and intrinsic insight. In their experiment, subjects

solved compound remote associate problems (a special kind of semantic association task)

and, on a trial-by-trial basis, indicated whether they achieved the solution via insight or

analysis. Immediately prior to insight solutions, subjects blink longer and look away from the

problem more frequently than prior to analytic solutions. Thus, they shift their attention away

from the visual stimuli towards internal processing. Salvi et al. (2015) used an experimental

paradigm similar to Jung-Beeman et al. (2004) who recorded high density EEGs while

subjects solved compound remote associate problems. Relative to analysis, the authors find

more alpha band activity around 9.8Hz at right parietal regions for insight from -1.4 to -0.4s

before the solution response. An increase in alpha power is traditionally believed to reflect

cortical idling or cortical inhibition (for reviews, Pfurtscheller, 1999; Pfurtscheller et al.,

1996). Consequently, enhanced alpha power over the parietal-occipital cortex indicates idling

or inhibition of the visual cortex, wherefore Jung-Beeman et al. interpret their alpha effect as

a selective gating of visual inputs to the right hemisphere that allows weaker processing

about more distant associations to gain strength (cf. Jung-Beeman et al., 2004). Taken

together, intrinsic insights are preceded by an increase in alpha power over right parietal


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regions, they are associated with an increased internal focus of attention and involve a weak

and unconscious pre-activation of solution-related information within the right hemisphere.

We assume that extrinsic insights initially involve the same processing as intrinsic insights: a

weak activation of solution-related concepts combined with a strong activation of obvious but

misleading problem-related information. This hypothesis is supported by a study of Bowden

and Jung-Beeman (2003a) revealing a connection between extrinsic insight, the right

hemisphere and solution priming. The authors used a similar experimental paradigm to the

one in a previous study (1998): Their participants worked on a verbal problem, they were

confronted with a target word that was either the solution or an unrelated word, they named

the target word and decided whether it represented the correct solution. Additionally, they

rated if they recognized the solution with or without “aha” moment. As expected, following

unsolved problems, the participants exhibited more solution priming for solutions that they

later recognized with insight than for solutions that they recognized without it. This

association was even stronger for solutions that were presented to the left visual field.

Consequently, both extrinsic and intrinsic insight seem to involve an unconscious pre-

activation of solution-related information within the right hemisphere.

However, while intrinsic insight involves an attention shift away from the visual stimuli

towards internal processing, extrinsic insight may require the exact opposite. In terms of

CRAs, solution generation differs from solution recognition, because the problem solver is

confronted with the solution word itself and just needs to draw the right connections between

the problem words and the solution. Assuming that these connections are already weakly

activated for insightful solution recognition, there is no need for a shift of attention. Instead,

the problem solver shall maintain a rather externally oriented attention towards the visual

stimulus, i.e. the solution.

For analytic solution recognition, no evidence for such a specific, unconscious pre-activation

of solution-related information within the right hemisphere is found. To be more precise,

participants showed less solution priming for analytic than for insightful solution recognition

and there was no difference between the hemispheres (cf. Bowden and Jung-Beeman, 2003a).

Consequently, participants need to engage in a more active search to find out how the

solution word forms a compound with each of the three problem words. We assume that this

active search for associations results in an inhibition of visual input reflecting an increased

internal focus of attention. Accordingly, we expect more alpha power over right parietal


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regions prior to analytic than prior to insightful solution recognition. In other words, we

presume that intrinsic and extrinsic insight have the opposed effect on alpha power.

Consequently, a cross interaction between modality, i.e. solution generation or recognition,

and problem solving strategy, i.e. insight or analysis, is anticipated.

2 Materials and Methods

To explore the differences and similarities between extrinsic and intrinsic insight

systematically, the experimental paradigm of Jung-Beeman et al. (2004) was modified. As in

their study from 2004, subjects worked on verbal puzzles, so-called compound remote

associate problems (CRA). They were asked to respond with a bimanual keystroke as soon as

they found a possible solution and to indicate whether they solved the problem with or

without “aha” moment. Unlike Jung-Beeman et al. (2004), we gave participants 20s instead

of 30s to solve a problem. A pilot study showed that approximately 50% of the problems are

solved within this time limit. This was important for our study, because subjects were not

only asked to actively solve a problem but also to passively recognize its solution if they

exceeded the time limit. Hence, if a participant failed to respond within 20s, the problem

words disappeared and the solution word was presented. To assure comparability (all CRAs

were solvable) and due to the limited number of trials, all solution words were accurate.

However, participants were not aware of their correctness. They were instructed to respond

with a bimanual keystroke only if (and at the same time as soon as) they understood the

displayed solution and to specify whether they felt an “oh yes” experience when recognizing

it. That way, time segments prior to these keystrokes could be analyzed and the insight-

specific activity of solution generation and recognition could be contrasted.

2.1 Subjects

Twenty-four right-handed, healthy native German speakers participated voluntarily in the

experiment. The eleven female and thirteen male subjects were aged between 19 and 28 and

received 8 euros per hour as expense allowance. Prior to the experiment, all participants

completed a screening questionnaire such that any neurological or psychological disorders, a

history of brain damage, substance abuse and medication could be ruled out. All experiments

were carried out in the morning and had a duration of approximately 90 minutes plus

preparation and follow-up. The study was approved by the ethics committee and all subjects

signed an informed consent form.


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2.2 Stimulus Material

In our experiment, native German speakers were confronted with a German version of the

compound remote associate problems introduced by Bowden and Jung-Beeman (2003b) who

adapted them from Mednick’s Remote Associates Test (c.f. Mednick, 1962). They consist of

three different problem words, for instance “age”, “mile” and “sand”, to which a fourth

solution word must be found. This solution word (in the example, “stone”) needs to form a

compound with each problem word (i.e. “stone age”, “milestone” and “sandstone”). CRA

problems are especially well suited to study insight experiences with neuroscientific methods

for a number of reasons. First of all, CRA problems can be solved with and without insight

such that the non-insight condition can be used as a baseline to extract insight-specific neural

activity. Since they are simpler than classical insight problems, a better control of confound

variables can be provided. For the same reason, they can be solved quickly such that a large

number of problems can be presented. Finally, they are physically compact which enables the

presentation on a computer screen and minimizes eye movement artifacts (cf. Bowden and

Jung-Beeman, 2003b).

To obtain a set of German compound remote associate problems, the English riddles were

first translated. If possible, this translation was directly used as a German CRA. If not, the

translation was adjusted whenever it seemed reasonable or replaced with a newly invented

German compound remote associate problem. Since German word compositions often

involve so-called joint elements1, some additional restrictions were made. Firstly, the German

word compositions should always consist of two autonomous words. Secondly, the subjects

should always be able to attach the solution word prior or post the problem word without

making any adjustments. Within these restrictions, 108 German CRA problems were

generated. Thereby, all solution words were unique. That means, they solved only a single

CRA problem and they were never used as a problem word.

2.3 Procedure

Initially, all subjects completed a training session with five German CRA problems.

Afterwards, questions concerning the experimental procedure were clarified and the 103 1For instance, the English compound “safety pin” equals the German compound “Sicherheitsnadel” that consists of the nouns “Sicherheit” and “Nadel” and the joint element “s”.


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remaining problems were presented in a random order in three consecutive blocks. Each

experimental trial started with the question “ready?” shown in the middle of a computer

screen. With an arbitrary keystroke a fixation cross appeared that was replaced after 500ms

by a German compound remote associate problem. The subjects had 20 seconds to solve each

problem and they were instructed to respond with a bimanual button press as soon as they

found a possible solution. With this keystroke, the three problem words disappeared and a

fixation cross was presented for five seconds. Afterwards, the participants had to decide

whether they solved the problem with or without “aha” moment on a three step scale, and

they were invited to pronounce their solution word. Finally, they were supposed to specify

how confident they were that their solution was correct ranging from “certain” to “fairly” and

“uncertain”.

Figure 1: Diagram showing the experiment procedure. The course of each trial depends on whether or not

a solution is generated within 20 seconds (first crossing point marked with a gray circle) and

whether or not a solution is recognized within 5 seconds (second crossing point).

If a problem could not be solved within 20 seconds, the word “timeout” appeared on the

screen for 1.5 seconds. Then, the solution word was shown and the subjects had to respond

with a bimanual button press as soon as they understood the presented solution. If they

reacted within five seconds, a fixation cross appeared for five seconds. Afterwards they had

to decide whether they recognized the solution with or without an “oh yes” experience on a

three step scale and the next trial started. If they failed to understand the presented solution


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within the five second time limit, the words “second timeout” appeared for 1.5 seconds

before the next trial started automatically. Figure 1 illustrates the whole experimental

procedure.

In compliance with Bowden and Jung-Beeman (2003b), all words were presented at the

center of a black screen in normal horizontal orientation in yellow (RGB colors: 255,255,0)

14 point Arial font in order to minimize eye movements. Moreover, all words that appeared

on the screen were capitalized to assure comparability2. Prior to the experiment, the

participants were familiarized with the differentiation between insightful and analytic

solution generation and recognition. To avoid any influences by the investigator, the

description length or other confounding variables, the instructions were presented in a written

form on the screen. They were based on the definitions used by Jung-Beeman et al. (2004)

and by Bowden and Jung-Beeman (2003b). Afterwards, the experiment participants were

asked to briefly recapitulate their own definition of intrinsic and extrinsic insight.

2.4 Exclusion Criteria

First of all, trials that included a premature verbalization of the solution, that showed reaction

times less than 100ms or that involved any other disturbances3 were removed from analysis.

Second, subjects that were unable to correctly classify the different problem solving and

solution recognition strategies were excluded. To this end, the participants’ descriptions of

insightful and analytical solution generation and recognition were compared with theoretical

criterions of insight and analysis. These theoretical criterions were derived from the

descriptions that Jung-Beeman et al. (2004) and Bowden and Jung-Beeman (2003a) used for

their insight judgment procedure. They addressed three different aspects: the nature of the

solution path (unawareness and suddenness versus awareness and strategic thinking),

confidence (obviousness versus the need to mentally check the solution) and affect (feeling of

“aha”). Subjects whose descriptions contradicted any theoretical criterion of insight or

2 This was necessary because some problem words were adverbs or adjectives that are usually written in lower case letters, while others were nouns that start with a capital letter in German.

3 For instance, interactions with the investigator.


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analysis, that named not at least one or that completely misunderstood the classification task4

were not included in any further analysis.

2.5 Behavioral Data Analysis

Initially, the response frequency was examined, i.e. the percentage of solutions derived via

insight or analysis, the percentage of solutions recognized with or without insight, the

proportion of correct and confident solutions, the amount of timeouts and the overall error

rate. Afterwards, differences in reaction time between insight and analysis were investigated.

Since each participant typically exhibited a different number of insightful and analytic trials,

the data was post-experimentally counter-balanced to assure comparability. That means, for

the predominant category, as many trials were chosen pseudorandomly as the less frequent

category provided. To receive sufficiently good estimates, a minimal number of five trials

was specified. Subjects who did not fulfill this criterion were excluded from the analysis of

reaction times (for an overview of the number of trials provided by each subject that was

included into analysis, see table A.1 in the appendix). For all other participants, the mean

response time of insightful and analytic solution generation and recognition was calculated.

With these individual means, two paired t-tests with significance levels of α = 0.05 were

performed: One examined differences in reaction time between insightful and analytic

solution generation, while the other one contrasted insightful and analytic solution

recognition. The assumption of normality was controlled by a Lilliefors test with a

significance level of α = 0.05.

2.6 EEG Analyses

63 electrodes were placed according to the extended 10-20 system and recorded with the

bridged mastoids as reference. Impedance was kept below 5kΩ. Moreover, the

electrooculogram was conducted consisting of two electrodes at the left and right side of the

eyes and two electrodes above and below the dominant eye. EEG analyses were performed

with BrainVision Analyzer 2 and Matlab, while some functions of EEGLAB were utilized for

the topographic mappings. The data was bandpass filtered with a passband from 0.1 Hz to

100 Hz and an initial automatic raw data inspection was performed. These preprocessing

steps ensured that neither slow drifts nor severe artifacts would affect the independent

4 For instance, some subjects confounded a lack of understanding with analytic solution recognition.


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component analysis that was carried out to correct eye movement artifacts. This ICA was

followed by a highpass filtering to 1 Hz and a second raw data inspection with more

conservative criteria that assured that no smaller artifacts contaminated the data. After this

preprocessing, breaks between the different trials were eliminated and the alpha band power

(8-13 Hz) was calculated using a continuous wavelet transform with a complex Morlet

wavelet.

To test whether intrinsic and extrinsic insights were preceded by opposed alpha effects, time

segments were extracted that started 2s prior to the insightful or the analytic generation or

recognition of a solution and ended 200ms after it. Thereby, trials with reaction times of less

than 2s were excluded. As an effect over right parietal sides was expected, electrodes P6, P8

and PO8 were identified as region of interest (ROI). If a time segment contained any artifact

within this ROI it was excluded from analysis. By visual inspection, a relevant time window

prior to solution generation and recognition was determined. As for the behavioral analyses,

the insightful and analytic trials were counter-balanced and a minimal number of five trials

was specified. Counter-balancing was particularly important for the present analyses, because

it assured comparable signal-to-noise ratios. For every subject that provided enough trials, the

insightful and analytic solution generation and recognition segments were separately

averaged and the mean within the specified time window and ROI was calculated. Since

power values are usually not normally distributed, the data was log-transformed to assure

normality. To assess modality-specific differences between insight and analysis, two paired t-

tests with significance levels of α = 0.05 were performed. Since less alpha band power was

expected for insightful than for analytic solution recognition, a left-tailed t-test was carried

out for this modality. In contrast, a right-tailed t-test was performed for solution generation,

because more alpha band power was anticipated for insightful than for analytic solution

generation. To test the interaction between problem solving strategy and modality, a repeated

measures analysis of variances was performed that included the factor “strategy” with the

levels “insight” and “analysis” and the factor “modality” with the levels “generation” and

“recognition”. For this particular analysis, the number of trials was counterbalanced not only

for analysis and insight but also for solution generation and recognition. As a matter of

course, only those subjects were included for whom enough trials were available in all four

conditions. As before, a significance level of α = 0.05 was chosen for all tests performed.


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3 Results

3.1 Exclusion Criteria

For intrinsic insight, all subjects were able to correctly classify insightful and analytic trials.

Only with respect to the (unnecessary) reexamination of an insight solution, some minor

deviations could be noticed: Three test persons expressed the compulsive need to internally

check their solution, while three other participants stated that they sporadically reexamined

their solution word. This possible response delay needs to be considered in the interpretation

of the results and also in the EEG signal analyses. Nevertheless, no subject had to be

excluded from analysis. For extrinsic insight, however, discrepancies between the subjects’

and the theoretical definition of analytical comprehension were detected. Five test persons

stated that they classified trials as analytical if they could not remember all three problem

words or if they did not understand the presented solution. Thus, they confounded a lack of

understanding with analytic solution recognition and had to be excluded from further

analyses.

3.2 Behavioral Data

In total, participants solved 51.2% of all the presented CRA problems. They classified 42.4%

of their solutions as insightful, 38.5% of their solutions as analytic and 19.1% as neither of

both. 19 of the 24 subjects performed the subsequent recognition task correctly. For problems

they failed to solve, these participants recognized 84.7% of the solutions. They classified

46.9% of their recognitions as insightful, 38.2% of their recognitions as analytic and 14.8%

as neither of both. The majority of the verbalized solutions were correct (87.9%), with an

even better accuracy for insightful solutions only (92.2%). Moreover, a connection between

insightful problem solving and confidence could be found: in 84.7% subjects were certain

that their insight solution was accurate, whereas for analytic solutions only 66.1% could be

achieved. This self-evaluation was appropriate since 96.1% of the confident solutions were

correct.


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Figure 2: Boxplots of the response times averaged over trials for insightful and analytic solution generation

(left) and recognition (right).

Obviously, solution generation and recognition differ with respect to their response times.

While the solution to 84.7% of the unsolved problems was recognized within five seconds,

just 51.2% of all puzzles could be solved within a time limit of 20 seconds. This difference is

neither astonishing nor surprising. However, the examination of reaction times also revealed

a commonality. Figure 2 shows the distribution of the grand means of the response times for

insightful and analytic solution generation (left graphic) and recognition (right graphic),

while table 1 contains the corresponding sample means. As can be seen, insightful responses

are on average faster than analytic responses for both solution generation and recognition. To

be more precise, subjects needed on average 6.67s to solve a problem via insight, whereas

9.44s were required for analysis. For insightful solution recognition, on average 2.34s were

sufficient, while 3.29s were spent for analytic comprehension.

Grand Mean

Insight Analysis t n df SD p Generation 6.67s 9.44s -7.07 22 21 1.84 0.0057 Recognition 2.34s 3.29s -6.77 19 18 0.61 0.0241

Table 1: grand means of the response times for insightful and analytic solution generation and recognition

along with the p-values of the corresponding t-tests, t-statistics, degrees of freedom, standard deviations

and n, the numbers of subjects included into analysis.

This observation is supported by the corresponding paired t-tests that became significant with

t(21)=-7.07, p=0.0057 for solution generation and with t(18)=-6.77 p=0.0241 for solution

recognition, respectively. A normal distribution of the difference variables could be assumed

since the corresponding Lilliefors tests revealed high p-values of 0.5. For solution generation,

Insight AnalysisGeneration

0

5

10

15

20

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onse

Tim

e in

ms

Insight AnalysisRecognition

0

1

2

3

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22 subjects provided the minimal number of trials, while 19 subjects fulfilled this

requirement for solution recognition. Table 1 summarizes the analyses of reaction times.

3.3 EEG Results

Like Jung-Beeman et al. (2004), we found more right parietal alpha band activity prior to

solutions that were derived via insight than prior to solutions that were solved by analysis.

This alpha effect lasted from approximately -2000ms to -1500ms before the solution. The

right graphic of figure 3 shows a topographic mapping of the alpha power difference (insight

minus analysis) within this time window, while the left graphic depicts the time course of the

mean alpha power within the specified region of interest.

Figure 3: left: topographic mapping of the alpha band power difference (insight - analytic) from -2000ms to -

1500ms prior to solution generation; right: alpha band power prior to solution generation averaged over

electrodes PO8, P8 and P6, trials and subjects for insightful (red) and analytic (blue) trials. The

associated standard errors are shaded in the corresponding color.

A right-tailed paired t-test confirmed the significance of this intrinsic insight effect with

t(21)=1.96, p=0.0318 (for more details, see table 2). To assure that this effect was no time

confound due to the different speeding of response times for insightful and analytic solutions,

we performed a second analysis that included only solutions with response times longer than

7s. For this subset of solutions, no differences in reaction time could be determined (t(16)=-

1.19, p=0.2506, α=0.05), whereas we still found significantly more alpha power for insightful

than for analytic solutions within the specified time window and ROI (t(16)=1.92, p=0.0362,

α=0.05; for more details, see table A.2 in the appendix).


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Grand Mean

Insight Analysis t n df SD p Generation 16.22µV2 13.50µV2 1.96 22 21 0.26 0.0318 Recognition 16.04µV2 22.76µV2 -2.42 15 14 0.40 0.0149

Table 2: grand means of the alpha power for insightful and analytic solution generation and recognition along

with the p-values of the corresponding t-tests, t-statistics, degrees of freedom, standard deviations and

n, the numbers of subjects included into analysis.

As anticipated, the opposite effect was observed for extrinsic insight. That is, less alpha

power was found prior to insightful than prior to analytic solution recognition within the

specified time interval and ROI (t(14)=-2.42, p=0.0149). Analogous to figure 3, figure 4

illustrates the topography of the alpha power difference (left subplot) and the alpha power

time course (right subplot) for solution recognition, while table 2 includes the corresponding

means, p-values, t-statistics, standard deviations, degrees of freedom and sample sizes.

Figure 4: left: topographic mapping of the alpha band power difference (insight - analytic) from -2000ms to -

1500ms prior to solution recognition; right: alpha band power prior to solution recognition averaged

over electrodes PO8, P8 and P6, trials and subjects for insightful (red) and analytic (blue) trials. The

associated standard errors are shaded in the corresponding color.

As for solution generation, this effect might be biased by the differences in reaction time.

Since the exclusion of fast recognitions could not balance the speed of responses, we cannot

replicate our findings for a subset of equally speeded recognitions. However, if the

differences in response time biased our results, there would be a significant difference

between fast and slow solution recognitions. To study this possibility in detail, we contrasted

the alpha power of immediate (response within 3s) and delayed solution recognitions

(response after 3s) balancing, of course, the number of insightful and analytic trials. For this

particular analysis, no minimal number of trials was set to maintain at least 13 subjects for


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analysis. We find no significant difference in alpha power between immediate and delayed

responses within the specified time window and ROI (t(12)=-1.31, p=0.2164 α=0.05, for

more details see table A.3 in the appendix). Due to the limited number of trials and subjects,

we further performed a repeated measures ANOVA that included strategy, i.e. insight or

analysis, as an additional factor. While neither the main effect of the factor reaction time, i.e.

immediate or delayed, nor the interaction between the factors becomes significant (F=2.24,

p=0.1600 and F=0.03, p=0.8576, respectively), the analysis reveals a significant main effect

of the factor strategy (F=18.10, p=0.0011). Hence, we are able to replicate our extrinsic

insight effect while factoring out the influence of the speed of responses (for more details, see

table A.4 and figure A.1 in the appendix). These results indicate that the difference in alpha

power prior to analytic and insightful solution recognition cannot be explained by the

differences in reaction time.

Figure 5: alpha power means of analytic (gray) and

insightful (black) solution generation (left

side) and recognition (right side) along with

their average (dotted line).

Source SS F p n Strategy 0.0002 0.0026 0.9598 15 Modality 0.1318 1.1265 0.3065 15 Interaction 0.7599 6.0622 0.0274 15

Table 3: Results of the 2-way repeated-measures

ANOVA: degrees of freedom (df) and means

of squares (MS) are not listed, because for

factors with just two levels df=1 and, with

this, SS=MS holds.

Furthermore, a two-way analysis of variance with repeated measures revealed a significant

interaction between the two factors “strategy” and “modality”, while none of the main effects

became significant. Table 3 comprises the corresponding p-values, sums of squares, F-

statistics and n, the number of subjects included into analysis, while figure 5 demonstrates the

associated alpha power means. Thereby, the mean analytic alpha power is depicted in gray,

while the mean insightful alpha power is colored in black. The average of the analytic and

insightful means is illustrated as a dotted line. Apparently, insight positively influences the

Generation RecognitionModality

16

18

20

22

24

Alp

ha P

ower

in 7

V2

Analysis Insight Average


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alpha power for solution generation, while it affects the alpha power for solution recognition

negatively. As illustrated by the dotted line, these opposite effects cancel each other out,

wherefore no significant main effect was obtained.

In addition to these findings, figure 3 and figure 4 show a crossover of alpha power for the

intrinsic (from approximately -800ms to -900ms prior to solution generation) and for the

extrinsic alpha effect (starting about 1000ms prior to solution recognition). Yet, an analysis

of the respective time intervals yielded no significant results.

4 Discussion

As repeatedly shown, compound remote associate problems can be solved with and without

insight. The present study replicates this result and demonstrates further prove that CRAs can

also be recognized in either an analytic or an insightful way. Moreover, the behavioral data

reveals significant differences with respect to analytic and insightful response times. For both

insightful solution generation and recognition, shorter mean reaction times are obtained. This

observation is in line with three other studies that reported shorter mean (or median) reaction

times for insightful problem solving than for analysis (cf. Kounios et al., 2006; Salvi et al.,

2015; Subramaniam et al., 2009). Unlike these authors, Jung-Beeman et al. (2004) cannot

report any differences in response time. As neither of the studies provide any information

about the reaction time distribution, this discrepancy might be a result of the longer time

period subjects had to solve each problem (30s instead of the 20s time limit in the present

study and the 15s time limit in the studies cited above). In conclusion, the observed

differences in reaction times provide additional evidence that insight and analysis represent,

in fact, two distinctive problem-solving strategies. As insight has a negative effect on

response times for both solution generation and recognition, the results emphasize,

furthermore, that intrinsic and extrinsic insight are subtypes of the same cognitive

phenomenon. Meanwhile, the different scaling of the extrinsic and intrinsic reaction times

already indicates that differences between the two insight subtypes exist.

This presumption is supported by electrophysiological findings. In accordance with Jung-

Beeman and colleagues (2004), we find significantly more alpha band activity prior to

insightful than prior to analytic solution generation at right parietal electrodes. While these

authors localize this intrinsic insight effect in a time interval from -1310ms to -560ms relative

to solution, we identify a corresponding effect a bit earlier, i.e. from -2000ms to -1500ms.


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This slight temporal shift might be the result of individual differences or response delays. As

mentioned in section 3.1., three of our subjects indicated after the experiment that they

always felt the need to mentally check their solutions, while two other participants admitted

to sporadically review their solution words. As hypothesized, we observe the opposed alpha

effect for extrinsic insight. That is, we find significantly less right parietal alpha power for

insight than for analysis from approximately -2000ms to -1500ms relative to solution

recognition. For both the intrinsic and the extrinsic insight effect, no indicators for a time

confound due to the different speeding of response times were found. Moreover, a repeated

measures ANOVA confirmed the hypothesis that intrinsic and extrinsic insight have an

opposite effect on alpha power with a significant cross interaction between problem solving

strategy, i.e. insight or analysis, and modality, i.e. solution generation or recognition.

In line with the results of Bowden and Jung-Beeman (2003a), we believe that both intrinsic

and extrinsic insight involve the same weak and unconscious pre-activation of solution-

related information within the right hemisphere. As pointed out by Jung-Beeman et al.

(2004), the insight-specific alpha power increase prior to solution generation may reflect a

selective gating of visual information that enables an increased focus towards internal

processing. This internal focus of attention strengthens the weak activation of non-obvious,

solution-related concepts that were overshadowed by the strong activation of obvious but

misleading problem-related information and allows them to emerge into consciousness.

Following this train of thought, the insight-specific decrease in alpha power prior to solution

recognition may reflect a rather externally oriented focus of attention towards the solution

word itself. Since the correct solution is presented and the information that is crucial for its

understanding is already weakly activated, no shift of attention towards internal processing is

necessary. In contrast, prior research does not suggest a comparable pre-activation of

solution-related information for analytic solution recognition. Thus, an individual needs to

engage in a more active search to find the right connection between the solution and the

problem words. This active search might be accompanied by an increased internal focus of

attention and the inhibition of visual information that is reflected in the enhanced right

parietal alpha band activity prior to analytic solution recognition. Thus, pursuing the

interpretation of Jung-Beeman et al. (2004), the opposed alpha effects for intrinsic and

extrinsic insight may suggest that the two phenomena are associated with opposed foci of

attention.


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However, an alternative interpretation is possible. While an increase in alpha power is

traditionally believed to reflect cortical deactivation or cortical idling (for reviews,

Pfurtscheller, 1999; Pfurtscheller et al., 1996), evidence accumulates that alpha

synchronization may also reflect top-down inhibitory control processes (for review, Klimesch

et al., 2007). As Klimesch et al. (2007 p. 63) point out: “ERS is elicited in situations, where

subjects withhold or control the execution of a response and is obtained over sites that

probably are under, or exert top-down control”. Consequently, the increase in right parietal

alpha power prior to intrinsic insights may also reflect the active inhibition of solution-related

information. This interpretation is in line with the theory that an ill-defined problem space is

a crucial component of insight experiences (for review, Knoblich et al., 1999). According to

the theory, an individual automatically generates an internal representation of a problem

situation that is biased by context, familiarity and past experience. This initial representation

activates potentially useful knowledge elements that implicitly define a problem space within

which an appropriate solution is sought. For insight solutions, this initial problem space does

not contain the correct solution. As a consequence, the problem solver encounters an

impasse. This impasse can be overcome by changing the initial problem representation and,

herewith, the defined problem space. Once the problem space contains the correct solution,

the problem can be solved easily resulting in the subjective insight experience (cf. Knoblich

et al., 1999). Thus, in terms of the problem space theory, the right parietal alpha power

increase prior to intrinsic insights may be interpreted as an active inhibition of knowledge

elements that lie outside of the (still ill-defined) problem space. Accordingly, the decrease in

right parietal alpha power prior to extrinsic insight might represent the activation of

knowledge elements that were previously suppressed. This interpretation is supported by the

localization of the effects because the right hemisphere performs the coarse semantic coding

that is required to solve or understand a compound remote associate problem (cf. Beeman,

1993; Chiarello et al., 1990).

To determine if the opposed alpha effects reflect opposed inhibitory processes and/or

opposed foci of attention, further research is required. For instance, an eye movement study

could provide direct evidence for a relationship between extrinsic insight and an increased

external focus of attention (cf. Salvi et al., 2015), while the analysis of functional couplings

between parieto-occipital and prefrontal areas could provide further insights into the

involvement of top-down processes (cf. Sauseng et al., 2005).


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5 Conclusion

This study is the first to investigate the differences and similarities between intrinsic and

extrinsic insight on a behavioral as well as a neurophysiological level. As a matter of fact,

intrinsic and extrinsic insight share some general characteristics. On the one hand, they both

lead to shorter mean reaction times than their analytic counterparts. On the other hand, a

neural correlate within the alpha frequency range can be determined for both that coincides in

terms of timing and localization. These findings indicate that the intrinsic “aha” and the

extrinsic “oh yes” moment are, in fact, two subtypes of insight experiences rather than two

completely independent cognitive phenomena. However, the disparate scaling of the extrinsic

and intrinsic reaction times and the opposite directions of the aforementioned alpha effects

also suggest that both subtypes differ substantially. While intrinsic insights are preceded by

an increase in alpha band power over right parietal regions, extrinsic insights are preceded by

a right parietal alpha power decrease. These opposed alpha effects may reflect opposed foci

of attention or, alternatively, opposed inhibitory processes. Regardless of the interpretation of

the effects, our results provide strong evidence that intrinsic and extrinsic insights differ on

the behavioral as well as the neurophysiological level. Thus, they have crucial implications

for the design of prospective insight experiments and the interpretation of recent research.

Instead of treating the intrinsic “aha” and the extrinsic “oh yes” as interchangeable, they

should be taken for what they are: two distinguishable subtypes of insight experiences that

share some characteristics but that need to be investigated separately. In conclusion,

Archimedes’ principle would have been uncovered either way: if someone had told him the

solution or if he had discovered it all on his own. Archimedes’ brain, however, would

probably have known the difference.


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Appendix

Solution Generation Solution Recognition

Reaction Time Alpha Power Reaction Time Alpha Power Alpha Power

Subject I A t-test I A t-test I A t-test I A t-test ANOVA 1 31 28 28 29 28 28 17 16 16 6 11 6 6 2 13 18 13 6 14 6 11 20 11 5 7 5 5 3 14 23 14 14 23 14 19 19 19 12 16 12 12 5 36 14 14 34 13 13 11 19 11 8 18 8 8 6 14 16 14 14 15 14 25 16 16 12 15 12 12 8 18 23 18 18 23 18 15 13 13 14 13 13 13 9 21 34 21 21 34 21 - - - - - - 21

10 25 19 19 25 19 19 19 7 7 - - - 19 11 30 6 6 30 6 6 28 13 13 16 10 10 6 12 18 23 18 17 15 15 27 19 19 21 14 14 14 13 11 12 11 11 12 11 31 19 19 15 12 12 11 14 13 23 13 13 19 13 23 18 18 - - - 13 15 13 15 13 12 15 12 40 14 14 5 12 5 5 16 32 14 14 31 13 13 - - - - - - 13 17 24 26 24 23 26 23 19 18 18 6 17 6 6 18 33 24 24 32 24 24 - - - - - - 24 19 24 33 24 22 29 22 6 35 6 - - - 22 20 28 15 15 26 14 14 29 7 7 12 7 7 7 21 29 16 16 28 16 16 6 25 6 - - - 16 22 26 22 22 25 21 21 34 5 5 15 5 5 5 23 12 28 12 12 25 12 8 13 8 5 11 5 5 24 20 18 18 19 18 18 21 21 21 14 16 14 14

Table A.1: Overview of the number of trials provided by each subject included into analysis for the different

conditions and tests that were carried out. The abbreviation “I” stands for insight and “A” for analysis.

Grand Mean

Insight Analysis t n df SD p Reaction Time 11.21s 11.86s -1.19 17 16 2.23 0.2506 Alpha Power 14.93µV2 11.23µV2 1.92 17 16 0.43 0.0362

Table A.2: grand means of the reaction times and the alpha power for insightful and analytic solutions with

responses longer than 7s along with the p-values of the corresponding t-tests, t-statistics, degrees of

freedom, standard deviations and n, the numbers of subjects included into analysis.


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Grand Mean

Immediate Delayed t n df SD p Alpha Power 17.60µV2 22.40µV2 -1.31 13 12 0.45 0.2164

Table A.3: grand means of the alpha power for immediate (reaction time shorter than 3s) und delayed

solution recognitions (reaction time longer than 3s) along with the p-values of the corresponding t-test,

the t-statistic, the degree of freedom, the standard deviation and n, the number of subjects.

Source SS F p n Strategy 3.7475 18.104 0.0011 13 Modality 0.4792 2.2438 0.1600 13 Interaction 0.0048 0.0336 0.8576 13

Table A.4: grand means of the alpha power for immediate (reaction time shorter than 3s) und delayed

solution recognitions (reaction time longer than 3s) along with the p-values of the corresponding t-test,

the t-statistic, the degree of freedom, the standard deviation and n, the number of subjects.

Figure A.1: alpha power means of analytic (gray) and insightful (black) immediate (left side) and delayed

(right side) solution recognition along with their average (dotted line).

Acknowledgments

The authors would like to thank the Department of Psychology at the Humboldt-Universität

zu Berlin for their great support.

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New Insights into Insight: Neurophysiological Correlates ... · This paper will close this gap by examining the differences between the intrinsic “aha” and ... instance, the following

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