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Neuroscience Communications 2016; 2: e1126. doi: 10.14800/nc.1126; © 2016 by Kazuo Nishimura, et al.
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Individual differences in mental imagery tasks: a study of
visual thinkers and verbal thinkers
Kazuo Nishimura1, Takaaki Aoki2, Michiyo Inagawa3, Yoshikazu Tobinaga4, Sunao Iwaki5
1RIEB, Kobe University, Kobe, 657-8501, Japan; Santa Fe Institute, Santa Fe, New Mexico, 87501, USA 2Institute of Economic Research, Kyoto University, Kyoto, 606-8501, Japan 3Medical Welfare Center, St. Joseph Hospital, Kyoto, 603-8323, Japan 4Elegaphy, Inc., Otsu, 520-0225, Japan 5Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, 305-8566, Japan
Correspondence: Kazuo Nishimura
E-mail: [email protected]
Received: November 17, 2015
Published online: January 11, 2016
In the context of individual differences in human thinking patterns, the present study examined differences
between visual thinking and verbal thinking, specifically with regard to brain activity associated with each. In a
recent study, we divided subjects into visual thinkers and non-visual thinkers according to their responses to a
questionnaire survey, and took magnetoencephalogram (MEG) measurements while they underwent verbal and
visual tasks [1]. This revealed significant differences in brain activation patterns near both the primary visual
area and frontal language area, particularly during the verbal task [1]. From this, we surmised that human
original thinking can be divided into visual and verbal types. Our neurological analyses of the diversity of
individual thinking characteristics can likely be applied to the fields of economics and education.
Keywords: Visual thinkers and verbal thinkers; Mental imagery; Beta-band and gamma-band activities; Group
differences; Magnetoencephalography
To cite this article: Kazuo Nishimura, et al. Individual differences in mental imagery tasks: a study of visual thinkers and
verbal thinkers. Neurosci Commun 2016; 2: e1126. doi: 10.14800/nc.1126.
Copyright: © 2016 The Authors. Licensed under a Creative Commons Attribution 4.0 International License which allows
users including authors of articles to copy and redistribute the material in any medium or format, in addition to remix,
transform, and build upon the material for any purpose, even commercially, as long as the author and original source are
properly cited or credited.
Introduction
In the field of economics, neuroeconomics has received a
great deal of interest. This field examines economic behavior
and its association with accompanying brain activity by
integrating research in experimental economics and
behavioral economics, fusing them with that of neuroscience.
For example, one study of neuroeconomics found that the
prefrontal cortex is active when choices are made about the
distant future, while the limbic system of the cerebrum is
active when choices are made about the near future [2]. In
other words, different regions of the brain are used when
making choices pertaining to the near versus distant future.
These studies seem to take the approach of obtaining the
overall perspective concerning the average human being.
However, conventional economics places a strong
emphasis on conducting studies that address resource
distribution in a society comprising heterogeneous agents [3].
Individuals can be divided into two completely different
groups of risk lovers and risk averters based on attitudes
toward danger [4]. In game theory, some have studied
RESEARCH HIGHLIGHT
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interdependent relationships such as conflicts of interest or
collaboration between different individuals, as well as
decisions on strategy [5].
In general, comprehension of another individual’s thought
process is difficult. The psychological state that would allow
one to stand in another’s shoes and understand him or her is
called the “theory of mind” in psychology [6]. The theory of
mind has been studied extensively in young children in their
formative stages, and in individuals with developmental
disorders such as autism spectrum disorder [7]. However,
given the diversity of individual personalities and demeanors,
even healthy individuals in the general population require
high level communication skills to grasp another’s
personality or sensitivities and interpret their emotional
dynamics. For example, we must collect information related
to another’s personality and actions, or predict long-term
their personality and sensitivities as the relationship develops
with time.
While the importance of distinguishing between
individuals based on differences in thinking patterns
(regardless of whether they are congenital or acquired) is
widely acknowledged, only a few studies have addressed
economic behaviors among different individuals. In
particular, studies that examine how differences in individual
thinking characteristics affect decision-making are incredibly
scarce. Against this backdrop, our research has focused on
understanding why different individuals end up making
different choices and how brain function differs in these
situations. We anticipate that research on thinking
characteristics and decision-making will form the foundation
for understanding judgments and decisions made by
consumers and investors regarding economic challenges.
Thinking comprises verbal thinking (using words to think)
and visual thinking (using images, rather than words, to
think), and some have studied differences between the two
using brain measurements [8]. In the same way that some
people can remember the faces of those they have just met,
while others cannot, individuals also vary in their capacity to
evoke images of certain things. It is known that individuals
who can remember a large amount of information in a short
period do so using visual images. When playing chess, a
professional chess player can evoke images of the patterns of
chess pieces and move their chess pieces accordingly without
verbalizing these thoughts. In general, these individuals use
more dominantly the right hemisphere of their brain over the
left hemisphere, as well as the visual area over the verbal
area. In addition to professional chess players, many who
work in design and imaging occupations share this tendency
toward visual dominance.
Individuals whose thinking is dominated by verbal
Table 1. Questionnaire and Tasks: Five-item questionnaire (a) was used to assess subjects’ ability to form
mental images. Tasks (b) were used in the experiment
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thinking tend to comprehend things in order. They have
difficulty starting a novel halfway through, or listening to a
mathematical lecture halfway through. These individuals
must read from the beginning, or listen from the start, in
order to understand the content. When they think, they think
while talking to themselves. This differs from visually
dominant thinkers, who think while moving images around.
In a recent study, we divided subjects into two groups
based on whether they had strong or weak visualization
ability to form mental imagery. We then proceeded to
examine how this ability at the time of thinking affected
global brain activation patterns, as well as differences in
local activation patterns that emerged in a region of interest
(ROI) [1]. With the prediction that the strength of
visualization ability is associated with a tendency toward
visual or verbal thinking, we hypothesized that “when
undergoing a visual or verbal task, those with strong imaging
capacities will have more activation in the visual area, while
those with weak imaging capacities will show more
activation in the frontal language area, as assessed with
high-β and low-γ bands.” To test this hypothesis, we
administered block design tasks to our subjects and
conducted magnetoencephalography (MEG) using SQUID.
This experimental task has been used in previous studies [9-11].
Subjects were divided into groups according to whether they
had strong or weak visualization abilities using a survey
developed in a previous study that uses visual and verbal
factors to classify individuals in this manner [8]. The survey
we used was created independently, but was based on
essentially the same principle [9-11]. Comparison of brain
activity in the two groups revealed that those with strong
visualization ability tended to be visual thinkers, while those
with weak visualization ability tended to be verbal thinkers.
Below, we will discuss the research in light of results from
our recent paper, together with some complementary findings [1].
Materials and methods
Experiments were conducted on four dates from August 2
through September 13, 2011, at the National Institute of
Advanced Industrial Science and Technology in Ikeda City
(Osaka, Japan). Individuals subject to analysis totaled 13 (11
males, 2 females), and were divided ahead of time into two
groups according to their dominant thinking pattern as
determined by the survey. Actual question items used to
divide subjects are shown in Table 1(a). For each “A”
selected for any of the questions, the respondent received 1
point, and each “B” received 0 points. Those who chose
more “A”s than “B”s (i.e., had a total score of 3 or higher)
were classified as Group I (strong visualizers). Those with a
total score of 2 or lower were classified as Group L (weak
visualizers).
Each experimental session comprised 2 back-to-back
repeated sequences in which a subject was asked to do the
following: envision Kiyomizu-dera (a famous temple in
Kyoto), envision the Japanese House of Parliament, recall the
12 signs of the Chinese zodiac, recall a conversation they had
with someone that day, and cease thinking at rest (Table 1b).
Ten seconds was allotted to each task, with no breaks in
between. The reasoning behind each task was as follows:
envisioning Kiyomizu-dera and the Japanese House of
Parliament required them to imagine a book or photograph
(1, 2). Recalling the 12 signs of the Chinese zodiac led them
to chant nouns in their head (3). Recalling a personal
conversation challenged them to remember an encounter with
someone (4). Tasks 5 and 6 were done to have them rest. Our
intent was to measure neurological activity while subjects
were thinking as they performed tasks 1 and 2 for visual
imagery (hereafter, visual conditions) and 3 and 4 for verbal
recollection (hereafter, verbal conditions), and then compare
these measurements with those taken while subjects were
still and rest during tasks 5 and 6 (rest conditions) in order to
Figure. 1. SQUID sensor locations. Sensor Nos. v1 and v2 monitored visual areas. Sensor Nos. b1, b2 and b3 monitored frontal language areas. More specifically, Nos. v1 and v2 designate primary visual and early visual areas, respectively. Nos. b1, b2 and b3 designate frontal language areas in
the middle frontal gyri (b1) and in the left inferior frontal gyri (b2 and b3). No. b3 corresponds to so-called Broca’s area.
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identify any increases in measurements relative to those at
baseline (tasks 5 and 6).
A whole-cortex-type 122-channel direct current SQUID
system (Neuromag 122, Elekta-Neuromag, Helsinki,
Finland) was used for MEG measurements. Several groups
have published protocols, theorems, and spectrum analyses
according to MEG [12-19]. For each channel, the MEG signal
was measured, and a short-time Fourier transform was
applied to each 1/5 second interval. We thereby derived an
estimated spectral density for all 61 sensor locations in 5 Hz
widths. For each condition (visual, verbal, and rest), means
for the two groups were determined. In order to examine
activation patterns under visual conditions and verbal
conditions relative to baseline, we calculated the mean ratios
of these measurements relative to the mean from the rest
conditions for each sensor.
Results
In this section, we will report some of our findings, with
new results on additional frequency bands and sensors [1].
Figure 2. Plots of the sensor-specific spectral densities under the visual condition (upper
row) and the verbal condition (lower row), for 27.5–32.5 Hz (central frequency: 30 Hz). Fig. 2 plots the sensor-specific spectral densities (the ratios) under the visual condition (upper row) and the verbal condition (lower row).They are relative to the resting condition. All figures represent the results
of nonparametric regression smoothing on the layout map as shown in Fig. 1. In order to improve the MEG measurement sensitivity for detecting global changes in neural activity, the spectral densities are normalized by the mean of densities of all sensors measured under the corresponding conditions. In each figure, the left-most images present the data for Group I, the middle images present the data for Group L, and the right-most images present the ratios of the Group I data relative to Group L data.
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Figure 1 shows the distribution of the 122 sensors made into
61 pairs. Figure 2 is a color-coded display of the low-γ band
(27.5 Hz-32.5 Hz, central frequency of 30 Hz) spectral
density for each sensor under visual conditions (upper panel)
and verbal conditions (lower panel) in each group, presented
as ratios to that for rest conditions. Group I is in the first row,
Group L is in the second row, and the ratio of Group I to
Group L is in the third row. For each of these figures,
smoothing by nonparametric regression was performed
according to the sensor layout map shown in Figure 1.
In rows 1 and 2 of Figure 2, Group I and Group L both
show activation from the parietal region to the frontal lobe
under both visual and verbal conditions, and represent
“thinking” characteristics. In addition, as shown in row 3 (far
right), the left side near the visual area of Group I shows
more activation (reddish tint) relative to that of Group L.
This suggests that relative to Group L, those in Group I
(visual thinkers as defined by the survey) had more neural
activity near the visual area. Observations of the frontal
language area, which is located within the middle frontal gyri
and left inferior frontal gyri, revealed more activity in Group
L (bluish tint). The high-β bands (22.5 Hz-27.5 Hz, central
frequency of 25 Hz) showed a similar tendency to that of
low-γ bands (central frequency 30 Hz). For more on this,
refer to Figure 1 of our recent study [1].
From among the sensors thought to be near the visual
area and frontal language area, we selected some from each
area (Figure 1): v1 and v2 from the visual area and b1, b2,
and b3 from the frontal language area. The primary visual
area and early visual area were indicated by v1 and v2,
respectively. Frontal language areas in the middle frontal
gyri were indicated by b1, while those in the left inferior
frontal gyri were indicated by b2 and b3. In particular, b3 in
the left inferior frontal gyri corresponded to Broca’s area.
Figure 3 shows the Group I spectrogram (ratio against
Group L) for sensors v1, b1, and b3 for visual and verbal
conditions. The y-axis of the spectrogram shows the
frequency (9 frequency bands, central frequency of 10-50
Hz), while the x-axis shows the measurement time (0-20/3
sec). The y-axis is divided into 5 Hz intervals, and the x-axis
into 1/15 sec intervals, presenting a color-coded version of
spectrum density (ratio). Information on sensors v2 and b2
can be found in Figure 3a of our recent study [1].
Figure 3. Temporal variations of spectral densities in the ROI’s (visual and frontal language areas). Spectrograms represent the spectral intensities (the ratios) of the major regions of interest (v1: primary visual area, b1: frontal language area in the middle frontal gyri, and b3: Broca’s area) for Group I relative to Group L. The horizontal axis designates the measurement time (interval 1/15 second, total duration 20/3 seconds). The vertical axis designates the central frequency of the frequency bands (overall range of the central frequency 10–50 Hz, with steps of each 5 Hz wide). The left column presents the data under the visual condition, and the right column presents the
data under the verbal condition.
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Sensors in the visual area show an overall reddish tint, and
are consistent with the results of Figure 2, as they indicate
more activity in Group I. Particularly for v1, β bands with
central frequencies of 20 and 25 Hz (y axis) show a more
highly activated band (reddish) in the direction of the x-axis
(time). This corresponds to our previous observation of the
presence of low-γ band activity (around 30 Hz) during image
processing [20]. On the other hand, compared to sensors in the
visual area, those in the frontal language areas show an
overall bluish tint, with Group L showing markedly higher
activation, particularly under verbal conditions. Sensors b1
and b3 in particular show band-like areas of higher activation
(more blue) in the direction of the x-axis (time), specifically
for high-β/low-γ bands (y-axis) with central frequencies of
25 and 30 Hz.
Next, for sensors v1 (primary visual area) and b3 (Broca’s
area), we evaluated group-dependent differences in activation
patterns of the high-β band (25 Hz) and low-γ band (30 Hz)
under both conditions, testing for both fixed and random
effects. We also conducted a 3-D current source estimation
of brain activity using a spatial filter, and assessed
group-dependent differences in the primary visual area
(BA17) (MNI coordinates: [6-75-6] (mm)) and Broca’s area
(BA44) ([-51 27 18] (mm)) using fixed effects analysis.
Many previous studies have published on source localization
using MEG data [21-25].
Statistical analysis revealed that for both the sensor-based
and spatial filter-based approaches, consistent findings
obtained are as follows. Group I showed more activation in
the visual area compared to Group L, markedly so for the
high-β band (25 Hz). Group L showed more activation in the
frontal language area than Group I, markedly so for the low-γ
band (central frequency, 30 Hz).
Discussion
Group-dependent differences in global activation patterns
The present study aimed to demonstrate that individuals
who use more imaging in their spontaneous thinking show
more activity in the visual area when undergoing tasks,
relative to those who use less imaging. Research using fMRI
has found a significant correlation between an individual’s
subjective “vividness” of visual imagery and activity in the
visual area [26]. In addition, visual imagery activities involve
not only the visual area but associated areas from the frontal
lobe to the parietal area, involving activation of these areas as
well [27]. Our analysis revealed activation, not only in the
low-γ bands (central frequency 30 Hz; Figure 2), but for α, β,
and γ bands in the region spanning the frontal lobe to parietal
area. This was observed in both groups, regardless of visual
or verbal conditions (Figure 2, rows 1, 2). On the other hand,
both groups showed reduced activation near the visual area
(areas centered around sensor pairs v1 and v2) under both
conditions [1]. For both visual and verbal conditions, the ratio
of Group I to Group L revealed more activation in Group I
(Figure 2, row 3). We therefore conclude that our hypothesis
was supported, as Group I had higher activity than Group L
in the occipital area including the visual area while
performing the tasks. This result was consistent with that of
our previous study [9].
Importance of β and γ bands for spontaneous imagery
One study examined α (8-14 Hz) and β (14-24 Hz) band
brain activity during visual imagery [28]. During visual
imagery resulting from external stimulation, increased
activity is evident for θ waves and β waves in the frontal lobe
(particularly the medial superior frontal gyrus), as well as α
waves and β waves of the parietal area (particularly the
superior parietal lobe) [27]. In addition, γ bands play an
important role in higher brain function, especially in visual
cognition [29, 30]. Other research studies using EEG/MEG
have demonstrated that high-β bands and low-γ bands are
appropriate indicators that can be used to evaluate the degree
of individual competency with regard to visual and verbal
task processing [20, 31-33].
The present study analyzed α waves (central frequency 10
Hz), β waves (central frequency 15, 20, 25 Hz), and γ waves
(central frequency 30, 35, 40, 45, 50 Hz) (see spectrogram in
Figure 3a and Supplementary Figures from our recent study [1]). This revealed that Group I had higher activation with
regard to α waves, but particularly the high-β bands (central
frequency, 25 Hz) and low-γ bands (central frequency, 30
Hz) in the occipital area including the visual area.
Visual condition for visual imagery and verbal condition for
verbal recollection
While it is certainly necessary to distinguish between
perception of external stimuli and spontaneous imagery, the
two share similarities (in particular, activity near the visual
area) as well as differ with regard to brain activity [28, 34-40].
We focused on spontaneously occurring thinking, and
divided this into visual thinking and verbal thinking. The
visual thinking considered here is that which creates images,
while verbal thinking is that comprising self-talk. Some
studies have analyzed visual thinking and verbal thinking as
they relate to the strength of an individual’s ability for
imagery [1, 8, 41-43]. One such study examined the interaction
between activity in the frontal cortical area and that in
Wernicke’s area during verbal thinking [41]. We found,
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especially under verbal condition, that Group I showed
higher activation in the visual area associated with visual
cognition, while Group L had higher activation in the frontal
language area associated with verbal expression in the
middle frontal gyri and left inferior frontal gyri. This
indicates that strong visualizers are visual thinkers, while
weak visualizers are verbal thinkers. In other words, this
study presents evidence for an association between one’s
ability for mental imagery and brain activity.
Conclusions
Compared to measurement of neural activity evoked by
external stimuli of the visual or auditory organs, measuring
spontaneous neural activity has been considered difficult.
However, the present study used a SQUID device that
enables highly sensitive and non-invasive measurements of
spontaneous brain activity, which allowed for successful
examination of individual differences.
Specifically, global activation patterns for spontaneous
thinking activities revealed that strong visualizers showed
marked differences in brain activity from weak visualizers.
When the analysis was limited to a region of interest (ROI),
the group with strong visualization showed activation near
the visual area, while the group with weak visualization
showed activation near the frontal language area.
It is easy to imagine how an individual’s thinking pattern
(visual or verbal) might greatly affect that individual’s
thinking in everyday life. The present study demonstrates
that these individual characteristics would significantly
correlate with changes in global brain wave activity as well
as local activation patterns. We anticipate that these findings
will be applicable to fields related to economic activity and
education.
Conflicting interests
The authors have declared that no competing interests
exist.
Acknowledgements
We thank the editors of the journal for useful suggestions.
This work was supported by Japan Society for the Promotion
of Science, Grant-in-Aid for Research #23000001 and
#15H05729. This article contains Table 1 and some figures
with legends of the article and supplementary materials of
our paper in Neuroscience Letters, although figures are
slightly modified [1].
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