2012. Vol.3, No.1, 65-69
Published Online January 2012 in SciRes (http://www.SciRP.org/journal/psych) http://dx.doi.org/10.4236/psych.2012.31011
Copyright © 2012 SciRes. 65
Event-Related Potential Effects Associated with Insight Problem
Solving in a Chinese Logogriph Task
Qiang Xing1*, John X. Zhang2, Zhonglu Zhang1
1Department of Psychology, Guangzhou University, Guangzhou, China
2Department of Psychology, The Chinese University of Hong Kong, Hong Kong, China
Received September 30th, 2011; revised November 5th, 2011; accepted December 7th, 2011
The electrophysiological correlates of insight and non-insight problems solving were studied using event-
related potentials (ERPs). Participants were given some time to guess Chinese logogriphs and then pre-
sented with an answer to judge whether it matched the logogriph. Results showed that the insight trials
elicited a more negative ERP deflection (N300-500) than did the non-insight trials in most scalp regions.
In a later time window from 600 ms to 1100 ms, the insight trials elicited a more positive ERP deflection
(P600-1100) than the non-insight trials, mostly in central regions. The results indicate that the early
N300-500 effect may reflect cognitive conflict resulting from the breaking of mental set and the later
P600-1100 effect may be related to the formation of novel associations, both crucial to the occurrence of
Keywords: N300-500; P600-1100; Insight; Event-Related Potentials; Chinese Logogriph
Early Gestalt psychologists coined the term “insight” to refer
to the observation that the process of problem solving was not
trial-and-error but sudden understanding of the gestalt combi-
nation of the problem elements. Insight has been generally cha-
racterized with the following features, 1) Problem solvers usu-
ally meet with a primary impasse in their first attempt to solve
the problem, 2) The process of insight problem solving is
non-verbal, 3) The occurrence of insight is momentary with a
strong “aha” experience (Beeman et al., 2004).
Studies about insight were mostly performed with behavioral
paradigms until the beginning of the 21st century when resea-
rchers started to examine the neural mechanism of insight with
brain imaging techniques such as functional magnetic resonan-
ce imaging (fMRI) and event-related potentials (ERPs). Luo et
al. (Luo, 2004) for the first time studied insight with fMRI and
observed activation in a number of regions during insight prob-
lem solving, including frontal cortex, temporal cortex, anterior
cingulate cortex (ACC) and hippocampus. They suggested that
the breaking of a mental set, crucial to the occurrence of insight,
depends on ACC and left lateral prefrontal cortex, and that
hippocampus plays important role in the forming of novel asso-
ciations (Luo & Niki, 2003; Luo, Niki, & Phillips, 2004).
Bowden et al. found stronger activity in anterior superior tem-
poral gyrus (aSTG) when individuals solved insight problems
compared with non-insight problems (Bowden and Beeman,
2003 & 2007; Beeman, et al., 2004). Another study involving
similar contrasts revealed increased activity in precuneus, left/
middle frontal gyrus, occipital gyrus and cerebellum (Qiu, et al.,
2010). Apparently, insight involves more than a single region
(Luo, 2004). Research with ERPs has also been conducted to
reveal the electrophysiological substrates of insight (Qiu, et al.,
2008; Wang, et al., 2009).
Using the same catalyzed paradigm of Luo and NiKi (2003),
Mai et al. (2004) asked participants to guess a Chinese logo-
griph for some time before the correct answer was presented.
The ERP difference wave between the insight condition and the
non-insight condition revealed a negative component (N380)
with ACC as its neuro-generator, interpreted to reflect the brea-
king of mental set. Using the same paradigm, Qiu et al. (2006)
found a similar response called N320, also localized in ACC.
However, this N320 effect was found not only for the insight
condition but also for the condition where the answer was not
comprehenable. They suggested that N380, or N320 may not
reflect the breaking of mental set but just a generic cognitive
conflict the leve of which differs between familiar and new
ways of insight problem solving (Qiu et al., 2006).
This brief review indicates that insight involves complex
cognitive processes as reflected in activation in multiple regions
of brain (Luo, 2004; Qiu et al., 2008). For the electrophysio-
logical substrates of insight, there has been only one component
(N380 or N320) observed that may reflect the process of
breaking mental set or cognitive conflict (Mai et al., 2004; Qiu
et al., 2006). Although it is indispensable to break the mental
set in order to reach insight, the formation of novel association
may be crucial to insight as well (Bowden & Beeman, 2003 &
2007; Beeman, et al., 2004; Luo, 2004; Luo & Niki, 2003; Luo,
Niki, & Phillips, 2004), as insight is one form of creativity. So
far no study has looked at how novel association is reflected in
the ERPs. One possibility is that there are mulitple ERP re-
sponses under the catalyzed paradigm associated with breaking
mental set and new association formation. Thus, it is hypothe-
sized that an ERP response similar to N380 or N320 will be
elicited, which may reflect breaking mental set, later, some
more ERP effects would be observed which may be related to
new association formation.
In real life individuals often solve an insight problem at the
help of hints after a long time of exhaustive thinking, as de-
Q. XING ET AL.
scribed in the four-stage model of Wallas (1926). We intended
to use ERP to monitor this process of insight problem solving
by using the Chinese logogriphs, one of the typical insight ma-
terials. Early studies (Luo, 2004; Mai et al., 2004; Qiu et al.,
2006; Qiu et al., 2008; Wang et al., 2009; Qiu et al., 2010) in-
dicate that Chinese logogriphs are difficult because they contain
misleading information. Once the answer has been guessed,
individuals would feel a sudden “aha” experience.
As paid volunteers, 12 healthy undergraduates who were all
native Chinese speakers (6 females) aged 22 years - 24 years
(mean age = 23.4 years) participated in the experiment. They
are in the second year with the major of psychology. All were
right-handed with normal or corrected-to-normal vision.
As in Qiu et al. (2008), 150 pairs of hint logogriphs and tar-
get logogriphs were used as the materials. Similar to Qiu et al.
(2008) and Wang et al. (2009), the length of most logogriphs
was between 2 and 6 Chinese characters, while all answers
were a single character. The words that appeared in both the
questions and the answers were of high frequency. The charac-
ters were presented in the Song Ti font, at size No. 16. The hint
logogriphs were helpful for the guessing of target ones. For
example, the hint logogriph “有口难言 (meaning difficult to
say even having a mouth)” and the answer “哑 (meaning deaf)”
was paired with the target logogriph “有眼难见 (meaning dif-
ficult to see even having eyes)” and the answer “盲 (meaning
blind)” (for more details see (Qiu et al., 2008).
There were 4 phases in the experiment (shown in Figure 1).
Firstly, subjects were asked to try guessing the target logo-
griphs for 6 s. If they got an answer, they shall press the “1”
key to enter the fourth phase; if not, they shall not press any key.
After a 1 s interval, both the hint logogriph and the answer were
presented in the center for 4.5 s, and subjects were asked to
understand the relation between the hint logogriph and their
answer. They shall press the “1” key if they understood the
relation, and not press any key if they did not. The target logo-
griph was presented in the third phase for 6 s after a 1 s interval,
if subjects guessed the logogriphs, they were asked to press the
“1” key but to press no key if they did not. Finally, after 1 s
interval, pairs of the target logogriph and the answer were pre-
sented for 4 s, and subjects were asked to judge whether what
their guess was consistent with the correct answer or not, and to
press the “1” key if they got the answer right, or the “2” key if
they did not but understood the relation between the logogriphs
and the answers. They shall not press any key if they neither
guessed the logogriph nor understood the correct answer. Dur-
ing the last phase, the correctly guessed condition was regarded
as the non-insight condition. The condition where subjects un-
derstood the answer was referred to as the insight condition
according to early studies (Mai et al., 2004; Qiu et al., 2006). In
the non-insight condition, the feedback answer was consistent
with what participants guessed, insight did not occur when they
saw the answers, in contrast, in the insight condition, partici-
pants did not guess out the answers or had incorrect answers,
once they understood the standard answers after their presenta-
tion where an “aha” experience occurred (Mai et al., 2004).
To be familiar with the procedure and pace of the task, sub-
jects were trained with 10 trials using 10 pairs of practice logo-
griphs in the same procedure. The 150 pairs of test logogriphs
were evenly divided into 5 blocks with each pair of stimuli pre-
sented randomly without any repetition. Subjects could take short
breaks between two blocks. Subjects were seated in a quiet
room with the eyes being 70 cm away from the screen. They
were instructed to respond as quickly and accurately as possible
but avoid movements and blinks.
Brain electrical activities were recorded from 32 scalp sites
using tin electrodes mounted in an elastic cap (Brain Product)
with the reference located between the Fz electrode and the Cz
electrode. The vertical electrooculogram (EOG) was recorded
with one electrode placed above the right eye and the horizontal
EOG was recorded with the other electrode placed left at the
left eye. All the interelectrode impedance was maintained be-
low 5 kΩ. The EEG and EOG were amplified using a 0.05-80
Hz bandpass filter, continuously sampled at 500Hz/channel for
off-line analysis. Eye movement artifacts including blinks and
eye movements were rejected off-line. High frequency noise
was removed by applying a low-pass filter set at 16 Hz. Before
average, trials contaminated by blinks, eye movements and
excessive muscle activity (voltage over ±80 uv in any channel)
were rejected off-line. During averaging, all scalp-recorded ac-
tivity was digitally re-referenced to an average of the left and
right mastoids. ERPs following the onset of the answers (to-
gether with the target logogriphs) were analyzed within 1100
ms setting the pre-stimulus 200 ms period as the baseline.
EEGs of the correct guessing condition (the non-insight condi-
tion) and the understanding condition (the insight condition)
were averaged separately.
As observed from the grand-averaged waveform and topog-
raphical maps (Figure 2 and Figure 3), ERPs elicited by the
answer stimuli for the insight and the non-insight conditions
The flow of guessing logogriph procedure in each trial.
Copyright © 2012 SciRes.
Q. XING ET AL.
were clearly different from each other. The difference waves
were obtained by subtracting the averaged ERP of the non-
insight condition from that of the insight condition. Mean am-
plitudes in the time windows of 300 ms - 500 ms and 600 ms -
1100 ms were measured based on inspection of the grand-ave-
raged waveform and the topographical maps.
A negative ERP deflection (N300-500) was evoked in the
time window between 300 ms and 500 ms. Based in visual ins-
pection of the results and results in early studies (Mai et al.,
2004; Qiu et al., 2006), the following 13 electrodes were cho-
sen for two-way repeated-measures analyses of variance (ANO-
VA). The ANOVA factors were response type (insight; non-in-
sight) and brain scalp region [frontal (F3, F4, Fz), central (C3,
C4, Cz), parietal (P3, P4, Pz), fronto-central (FC1, FC2) and
centro-parietal (CP1, CP2) (the averaged ERP amplitude of
electrodes in each region was pooled)]. A positive ERP deflec-
tion (P600-1100) was elicited in the time window between 600
ms and 1100 ms, mostly in frontal, fronto-central and central
regions as shown in the topographical maps. So the following 8
electrodes were chosen for two-way repeated-measures analy-
ses of variance. The ANOVA factors were response type (in-
sight; non-insight) and brain scalp region [frontal (F3, F4, Fz),
central (C3, C4, Cz), fronto-central (FC1, FC2) (pooling elec-
trodes in each region)]. P-value of the analyses of variance was
corrected using the Greenhouse-Geisser method. The statistical
analyses were made in SPSS 13.0.
For the non-insight condition, the average number of guess-
ing the correct answer was 82 ± 18 and the reaction times were
1285 ± 324 ms. For the insight condition, the average number
of understanding the answer was 51 ± 17 and the reaction times
were 3097 ± 452 ms. The reaction times under the insight con-
dition were significantly longer than the non-insight condition,
F (1, 11) = 412.43, p < .001.
As shown in the grand-averaged waveforms and the differ-
ence wave map (Figure 2 and Figure 3), the early ERP com-
ponent (N1) was elicited under both the non-insight and insight
conditions, with no main effect of response type. However, the
insight condition evoked a more negative ERP deflection (N300 -
500) than the non-insight condition in the time window be-
tween 300 ms and 500 ms for most of the scalp regions. Later
within the 600 ms - 1100 ms window, a more positive ERP co-
mponent (P600-1100) was elicited under the insight condition
than the non-insight condition, salient in frontal, fronto-central
and central scalp regions. The mean ERP amplitudes for the
300 ms - 500 ms and 600 ms - 1100 ms time windows were se-
lected for statistical analysis below.
Two-way repeated-measures ANOVA showed that the main
effect of the response type reached significance in the 300 ms -
500 ms window, F (1, 11) = 16.51, p < .001. The main effect of
region was not significant, F (4, 44) = 2.67, p > .1. The interac-
tion effect was not significant, F < 1. Hence, the insight trials
elicited a significantly more negative ERP deflection (N300-
500) than the non-insight trials between 300 ms and 500 ms.
Between 600 ms and 1100 ms, there was no main effect for
response type or region, F (1, 11) = 2.46, p > .1, F (2, 22) =
Grand-averaged ERPs at Fz, Cz, C3 and C4 for the insight (long dotted
lines), non-insight conditions (short dotted lines), and the difference
wave (insight minus non-insight, solid lines).
Topographical maps of the voltage amplitudes for the insight vs.
non-insight difference wave in the 300 ms - 500 ms and 600 ms -
2.85, p > .1, respectively. The interaction between response
type and region was significant, F (2, 22) = 4.47, p < .05. Sim-
ple effect analysis showed that the insight trials elicited a more
positive ERP component (P600-1100) than non-insight over the
central regions, F (1, 11) = 5.05, p < .05.
Both the insight and non-insight conditions elicited an N1
showing no difference by response type. This result indicates
that N1 was related to the early visual processing that was com-
parable across the two conditions each involving the presenta-
tion of between 3 and 7 characters.
In later time windows, consistent with early studies, the in-
sight stimuli elicited a more negative ERP deflection (N300-
500) in the 300 - 500 time window than the non-insight stimuli,
similar to the N380 in Mai et al. (2004) and the N320 in Qiu et
al. (2006). Difference in the latency of the three ERP compo-
nents may be attributed at least partially to the differences of
the logogriph length.
As described in the introduction, it remains unclear as to
Copyright © 2012 SciRes. 67
Q. XING ET AL.
what cognitive mechanism this negative effect reflects, the
breaking of mental set (Mai, et al., 2004) or cognitive conflict
(Qiu, et al., 2006). In the catalyzed paradigm, subjects firstly
formed certain thought (the old thought). They then formed a
new thought if they understood the logogriphs or they did not
form any clear thought if they did not understand the logo-
griphs. Either way, they would experience transition from the
old thought to a new thought or to no thought at all, inducing
cognitive conflict. In the present study, the focus was on the
insight condition involving only comprehension, the conflict
from switching from an old thought to a new thought shall by
nature be related to the breaking of mental set.
Breaking mental set was regarded as one key cognitive proc-
ess of insight (Qiu, et al., 2010; Zhao, et al., 2011). Insight
problems such as the Chinese logogriphs task often involve
misleading cues, which make inappropriate constraints or un-
helpful primary knowledge strongly activated, leading to im-
passe where individual does not know how to solve this prob-
lem. Therefore, it is necessary to break the mental set in order
to solve the insight problem. However, insight as one form of
creativity involves another crucial cognitive component, the for-
mation of novel association (Bowden and Beeman, 2003 & 2007;
Luo, 2004) as well, therefore differences between the two com-
ponents lie in that the former emphasizes more the breaking of the
old and non-effective association while the later more on the
forming of new and effective association. Hence different ERP
components were observed in the time course of insight occur-
Beyond the early effects already reported in previous studies
(Mai et al., 2004; Qiu et al., 2006), the insight condition also
elicited a more positive ERP deflection (P600-1100) between
600 ms and 1100 ms in the present study, mostly in frontal, fron-
to-central and central regions (reaching significance in central
regions). No similar effects in P300 or late positive component
(LPC) had been observed for insight in early studies (Mai, et al.,
2004; Qiu et al., 2006). P300 and LPC shared many similarities
in latency and topographical distributions and were considered
related (Hajcak, Moser, & Simons, 2006; Huang & Luo, 2009).
LPC was found to be involved in attentional and orienting
processes (Knight; 1996; Hajcak, Moser, & Simons, 2006),
with its amplitude reflecting the amount of mental resources
employed (Olofsson, Nordin, Sequeira, & Polich, 2008). P300
was linked to memory updating, encoding, or retrieval, and the
formation of new representations through integration (Donchin,
1981), with its amplitude reflecting deployment of attentional
resources (Donchin & Coles, 1988). We suggest that when the
answers appeared, there was conflict between the new and old
thoughts under the insight condition, shown in the N300-500
effect. To correctly understand the answers of logogriphs, indi-
viduals needed to retrieve information related to the answer and
loose constraints of the old thought. When the retrieved infor-
mation was successfully integrated with the given answers fo-
rming a novel association or a new representation, the insight
occurred. P300 or LPC was sensitive to this process probably
because of the critical role of attentional resources in this proc-
ess. In conclusion, the P600-1100 effect might reflect the forming
of novel associations following the breaking of mental set.
In a word, the present ERP study showed that, compared
with non-insight problem solving, insight problem solving elic-
ited a negative deflection in the time window of 300 ms - 500
ms and a positive deflection between 600 ms and 1100 ms.
Therefore, the significance of this research is that the same
result was repeated that N300-500 may be related to the cogni-
tive conflict in the breaking of mental set, furthermore, P600-
1100 was discovered which may be related to the formation of
novel associations. So both N300-500 and P600-1100 may be
important electrophysiological labels in the process of insight
problem solving. However, there may be limitation as well as
significance. Similar to early studies (Mai et al., 2004; Qiu et
al., 2006), the catalyzed paradigm was employed in this study,
under which insight is externally elicited while internally pro-
duced insight would be neglected to some extent (Qiu et al.,
This work was supported by the National Natural Science
Foundation of China (31070918).
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