The Relationship between Psychological Workload and Oculomotor

Indices under Visual Search Task Execution

Tomomi Okano and Minoru Nakayama

School of Engineering, Information and Communications Engineering, Tokyo Institute of Technology,

W9–107, Ookayama 2–12–1, Meguro-ku, Tokyo, 152–8550 Japan

Keywords:

Eye Movement, Microsaccade, Pupil Diameter, NASA-TLX, Psychological Workload, Subjective Evaluation.

Abstract:

In this paper, we have focused especially on microsaccade and pupil diameter to extract relationships with

psychological workload. We measured how these oculomotor feature values changes to 10 subjects when

executing visual search tasks containing psychological workload. To evaluate the amount of psychological

workload, we used a systematic evaluation index, NASA-TLX and analyzed by combining pupil movements

with answer rate and difﬁculty of both tasks. As a result, we have discovered that by the difference of psycho-

logical workload and 2 experimental conditions, microsaccade frequency and task performance changes.

1 INTRODUCTION

Us human beings are constantly making eye move-

ments. Not only when moving our eyes while chang-

ing the point of view, but also while we are gazing.

The reason why we have constant eye movements is

because only a small portion of the retina in our eyes

have good vision, thus in order to perceive a visual

object clearly in the center of the retina, we need to

generate eye movements. Therefore, the eye move-

ment which shakes in small increments, are necessary

for us to maintain vision.

Have you ever experienced your eyes shaking bit

by bit when getting nervous? That is a kind of

an eye movement due to psychological workload,

hence there may be a close relationship between the

two. For example, pupil diameter is smaller when

parasympathetic nervous system is working to the ad-

vantage and larger when sympathetic nervous system

is as so. Throughan analysis of pupil size and salivary

amylase, when subjects are shown disgusting stim-

uli images, it shows that there is an association be-

tween stress and pupillary response. (Atsuhiko et al.,

2011) Moreover, there are other researches that de-

scribes the cellular activity of the rostral colliculus

in the midbrain, which is responsible for transmitting

oculomotor information as signals, is closely related

to generating microsaccade. Microsaccades and other

oculomotor features are strongly associated with psy-

chological workload.

Recently, innovative eye-based systems are being

developed, includingbiometric identiﬁcation and eye-

tracking technology. In order to promote the devel-

opment of an eye-friendly equipment in the future,

we believe that a feedback of psychological workload

of the operation is necessary.Variety of features such

as microsaccade, pupil size, and gaze time have been

proposed to objectively evaluate psychological stress

of users while using devices. In addition, because eye

movements can be measured without contact, it is ex-

pected to be an excellent indicator for objective eval-

uation. Through the study of changes in oculomotor

features due to psychological workload, the detection

of eye movement patterns during negative psycholog-

ical movements will help in the development of an

eye-friendly, smooth operative electronic devices.

Although we have noted that there has been many

similar studies linking microsaccade frequency and

psychological workload, there are still many un-

knowns. The general consideration of the relationship

between microsaccade frequency and psychological

workload is not clear since it has not used a system-

atic workload assessment. We created 2 experimen-

tal tasks with different presentation time and subjec-

tively evaluatedthem using NASA-TLX. The purpose

of this research are 2 points shown below.

• Clarifying the relationship between oculomo-

tor indices and psychological workload with a

systematic psychological workload assessment,

NASA-TLX.

• To examine effects of differences in presentation

time of various visual stimuli.

Okano, T. and Nakayama, M.

The Relationship between Psychological Workload and Oculomotor Indices under Visual Search Task Execution.

DOI: 10.5220/0010393403650371

In Proceedings of the 14th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2021) - Volume 4: BIOSIGNALS, pages 365-371

ISBN: 978-989-758-490-9

365

2 METHOD

2.1 Experimental Overview

In this research, we used 2 experimental tasks with

different stimuli presentation time to clarify the rela-

tionship between psychological workload and oculo-

motor features during task performance. Experiments

were conducted under the assumption that differences

in stimuli presentation time could be related to dif-

ferences in gaze area. The goal of the tasks were to

count the amount of speciﬁed ﬁgures to search for

in each question by looking at a screen with vari-

ous ﬁgures presented. Under the execution of experi-

ments, changes in psychological workload, microsac-

cade, and pupil size were investigated.

2.2 Experimental Tasks

In accordance with the purpose of experiment, 2 tasks

with different presentation time of the stimuli target

were created for observing eye movements caused by

psychological workload. By watching the screen with

several combination of ﬁgures, subjects were asked to

respond from 3 choices using the keyboard. In order

to keep the difﬁculty of the task linear, as the ques-

tion number increased by 1, the number of ﬁgures

displayed on the screen increased by 1, with the initial

value of 3 and 2 for Experiment 1 and 2 respectively

(See Table 1 for detail). To prevent microsaccades

from occurring due to excessive eye movements, a

cross was presented in the center of the screen as a ﬁx-

ation point and subjects were instructed to keep their

eyes on it as long as possible. Presentation time and

speciﬁc procedures of the stimuli in each experiment

are listed below.

2.2.1 Experiment 1

The ﬂow of presenting experimental stimuli in Exper-

iment 1 are as follows.

1. The ﬁgure asked to search for, 3 choices necessary

for answering, time limit are presented. When a

key is pressed by the subject, it switches to the

next slide.

2. A cross appears in the center of the screen for 1.0

second.

3. Various combinations of ﬁgures with overlap are

presented for 3 or 5 seconds(depends on the time

limit decided for each question). Subjects are able

to answer using the keyboard during this period of

time and when the answer is executed, it switches

to the next question.

Figure 1: Flow of Experiment 1.

To make subjects feel stronger psychological

workload, time limit was randomly set to 3 or 5 sec-

onds and there was no regularity for each question. 3

choices required for answering were also numerically

irregular. Figures that were presented were any com-

bination of 7 shapes, circles, triangles, squares, pen-

tagons, hexagons, heptagons, and octagons. Detailed

information about each question, time limit, and re-

quested ﬁgures to search for are shown in Table 1,

and the ﬂow of Experiment 1 is shown in Figure 1.

2.2.2 Experiment 2

The ﬂow of presenting experimental stimuli in Exper-

iment 2 are as follows.

1. The ﬁgure asked to search for, 3 choices necessary

for answering, time limit are presented. When a

key is pressed by the subject, it switches to the

next slide.

2. A cross appears in the center of the screen for 1.0

second.

3. For 0.5 seconds, various combinations of ﬁgures

are presented.

4. Cross ﬂash continues for 2.4 seconds. Subjects

are able to answer using the keyboard during this

period of time and the screen does not change

even if the response is given.

Same as in Experiment 1, Experiment 2 was a

task to count ﬁgures that were asked by looking at the

screen with various ﬁgures presented. The difference

of the two were the number of seconds ﬁgures being

presented and the timing of the subject’s responses.

Detailed information about each question, time limit,

and requested ﬁgures to search for are shown in Table

1, and the ﬂow of Experiment 2 is shown in Figure 2.

2.3 Experimental Devices

We used ViewPoint Eye Tracker 400 Hz Binocular

USB made by Arrington Research to measure eye

movements. Other devices such as the camera to mea-

sure the line of sight, infrared light irradiation device

that maintains brightness, jaw stand to ﬁx the position

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366

Table 1: Detailed information on experimental tasks.

Ques.No. Exp. Limit Amount Figure

Exp.1 3 3

Circle

Exp.2 - 2

Exp.1 3 4

Circle

Exp.2 - 3

Exp.1 3 5

Circle

Exp.2 - 4

Exp.1 3 6

Circle

Exp.2 - 5

Exp.1 3 7

Triangle

Exp.2 - 6

Exp.1 5 8 Square

Exp.2 - 7 Triangle

Exp.1 5 9 Heptagon

Exp.2 - 8 Square

Exp.1 3 10 Circle

Exp.2 - 9 Triangle

Exp.1 5 11 Hexagon

Exp.2 - 10 Pentagon

Exp.1 5 12

Circle

Exp.2 - 11

Exp.1 5 13 Circle

Exp.2 - 12 Triangle

Exp.1 5 14 Circle

Exp.2 - 13 Octagon

Exp.1 3 15 Circle

Exp.2 - 14 Square

Exp.1 5 16 Octagon

Exp.2 - 15 Circle

Exp.1 3 17 Triangle

Exp.2 - 16 Pentagon

Exp.1 3 18 Square

Exp.2 - 17 Heptagon

Exp.1 5 19 Pentagon

Exp.2 - 18 Triangle

Exp.1 5 20 Pentagon

Exp.2 - 19 Circle

Exp.1 5 21

Pentagon

Exp.2 - 20

Exp.1 5 22 Hexagon

Exp.2 - 21 Circle

of the head, Windows computer and keyboard to dis-

play stimuli and for answering were also used. Exper-

imental program was created using MATLABR2019a

and Psychtoolbox-3 was used to present experimental

stimuli.

Size of the display used was 336mm by 596.6mm

and we deﬁned the distance from the jaw stand to the

display as 530mm. Sampling rate was 420Hz, in or-

der to prevent the line of sight from changing signiﬁ-

cantly due to the vigorous eye movements of subjects,

graphic stimuli were set to ﬁt in 87 mm square in the

center of the screen within a visual angle of 10 deg.

Figure 2: Flow of Experiment 2.

Figure 3: Schematic diagram of 2 experiments.

2.4 Subjective Evaluation

To evaluate the degree of psychological workload, the

following rating scales were used to assess in both

experiments.

2.4.1 NASA-TLX

To evaluate psychological workload, we asked sub-

jects to answer a subjective survey based on NASA-

TLX, a systematic psychological workload scale. We

considered other types of psychological workload

evaluation method such as SWAT although we chose

NASA-TLX because it had various types of evalua-

tion scales.

NASA-TLX, the most commonly used subjective

workload evaluation scale, is a method to obtain the

ﬁnal workload as a numerical value by appropriately

weighting each 6 evaluation scales. For 6 speciﬁed

scales, there are line segments marked ”low” and

”high” at both ends and subjects were asked to mark

one point on the line segment where their feelings ap-

ply. The position of the mark is calculated as a raw

score. There is a calculation method of weight coef-

ﬁcients using one-to-one comparison method. How-

ever in this method, weighting coefﬁcients of items

that are not selected may be treated as 0, which leads

to calculation assuming with no contribution from

those items even though the raw score is not 0. There-

fore, we used a method to calculate weighting coefﬁ-

cients, by ranking each raw score. This method elim-

inates the possibility of items with a contribution of

The Relationship between Psychological Workload and Oculomotor Indices under Visual Search Task Execution

367

0, even though the raw scores are not 0. If the raw

scores are equal, the average of those ranks are taken.

From the ranking, weighting coefﬁcient of all items

are determined, with the highest raw score to 6, other

items in descending order. The numeric amount of

psychological workload can be calculated by divid-

ing the sum of the multiplication of weighting coefﬁ-

cient and raw score of each scale by 21(= the addition

of 6 numbers 1 to 6) (Shinji, 2015). 6 items used in

NASA-TLX are listed below.

• Mental Demand (MD)

• Physical Demand (PD)

• Temporal Demand (TD)

• Performance (OP)

• Effort (EF)

• Frustration Level (FR)

2.4.2 Psychological State Assessment Items

Psychological state was rated on a scale of 1 (very

low) to 5 (very high) for 6 items: difﬁculty, irrita-

tion, impatience, confusion, activity, and exhilaration,

based on the evaluation items in (Haruki Mizushina,

2011).

2.5 Experimental Procedure

A total of 4 experiments were conducted per subject

(2 for Experiment 1, 2 for Experiment 2). With 20

questions in both experiments, we were able to obtain

data of 80 trials per subject. After completing every

experiment, subjects were asked to ﬁll out a subjective

evaluation form about their psychological state to rate

how they felt. Since subjects needed to put off their

jaws from the jaw stand to answer the questionaire, in

order to prevent errors due to changes in the position

of the head and face when resuming, 9 points were

calibrated to conﬁrm whether the left eye was clearly

visible and to obtain accurate viewpoints each time

the experiment restarted.

Prior to the experiment, subjects were asked to ﬁll

out a consent form with full explanation of the exper-

iment. Informed consent was approved by the ethi-

cal committee of Tokyo Institute of Technology. (Ap-

proval number: A19054)

2.6 Subjects

Subjects were 10 undergraduateand graduate students

(5 males and 5 females) aged 20 to 23 years old. They

were conﬁrmed if they had proper eye sight (both

eyes above 0.8 (American style 20/25)) with naked

eye vision or corrected vision. In this experiment,

corrected vision was limited to contact lens wearers

since glasses may reﬂect unnecessary light.

3 RESULTS

3.1 Subjective Evaluation

The results of psychological workload analyzed us-

ing NASA-TLX are shown as a boxplot in Figure 4.

It shows the distribution of 6 scales and AWWL score,

which is the overall value of psychological workload.

From this ﬁgure, 3 items, mental demand (MD), tem-

poral demand (TD) and frustration level (FR), were

higher in Experiment 1 than in Experiment 2, while

the remainingthree items, physical demand (PD), per-

formance (OP) and effort (EF), were higher in Exper-

iment 2 than in Experiment 1. Furthermore, AWWL

score for Experiment 1 was higher than that for Exper-

iment 2. A two-tailed t-test at 5% signiﬁcance level

showed no signiﬁcant difference in AWWL score be-

tween the experiments, although there was a tendency

that Experiment 1 had stronger psychological work-

load than in Experiment 2.

Distributions of psychological state assessment

items in 2 experiments are shown in Figure 5 and re-

sults of a two-tailed t-test at 5% level of signiﬁcance

between 2 experiments for each items are shown in

Table 2. From Figure 5, most of the subjects gen-

erally found high load on difﬁculty and impatience.

Table 2 shows that there was a signiﬁcant difference

in exhilaration at 5% level of signiﬁcance between 2

experiments.

Figure 4: Subjective evaluation results in NASA-TLX for 2

experiments.

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368

Figure 5: Evaluation results in speciﬁc psychological state

indicators.

Table 2: T-test (two-tailed) for psychological state index of

each experiment.

Psychological State t df p

Difﬁculty 0.99 15.82 n.s.

Irritation -1.82 26.97 0.080

Impatience 2.04 24.07 0.052

Confusion -1.27 28.85 n.s.

Activity 0.25 25.45 n.s.

Exhilaration -2.91 21.27 < 0.05

3.2 Relationship between Psychological

Workload and Assessment Features

for Different Presentation Time

The relationship between AWWL score and 3 indices,

correct rate, microsaccade frequency, and pupil diam-

eter, were analyzed in each experiment. For anal-

ysis, the threshold of pupil aspect ratio was set at

0.75. Data below 0.75 were treated as blinks there-

fore we excluded them under the constraint that pupil

size were sufﬁcient for all subjects. For the analysis of

microsaccades, we utilized a method using the speed

of eye movements in (Ralf, 2006) (Ralf and Reinhold,

2003) (Ralf et al., 2015) and extracted those with am-

plitude less than 1 deg, maximum velocity of less than

200 deg/s to exclude saccades. The reference value of

pupil size was deﬁned as the average of pupil diame-

ters in the cross presentation (the ﬁrst 1.0 seconds of

each experiment). Table 3 shows the mean value of

correct rate, microsaccade frequency, and pupil size

of each experiment. A two-tailed t-test at 5% level of

signiﬁcance for 3 indices showed t(14.54) = − 4.44,

p < 0.05 for correct rate, t(18) = 3.76,p < 0.05 for

microsaccade frequency, that reveals signiﬁcant dif-

ferences due to experimental conditions. There was

Table 3: Mean values of 3 indicies in each experiment.

Correct Rate MS Freq. Pupil Ratio

Exp. 1 60.75 2.479 0.992

Exp. 2 73.00 5.779 0.995

Figure 6: AWWL score and correct rate.

no signiﬁcant difference in pupil diameter.

This result shows that microsaccade frequency is

higher in Experiment 2 than in Experiment 1. Since

microsaccade is an oculomotor feature that occurs

when gazing, one of the reasons for the increase of

microsaccade frequency in Experiment 2 may be be-

cause eye movements were suppressed in shorter pre-

sentation time since gaze area was relatively larger.

Figures 6 to 8 are scatter plots showing the rela-

tionship between AWWL score (an index of psycho-

logical workload) and correct rate, microsaccade fre-

quency, pupil diameter respectively in 2 experiments,

with the regression lines of the analysis of covari-

ance at 5% level of signiﬁcance for each. Black col-

ored triangles and squares represent the mean value of

AWWL score in Experiment 1 and 2. A table of anal-

ysis variance with equality tests for regression coef-

ﬁcients on correct rate, microsaccade frequency, and

pupil diameter for AWWL score are shown in Table 4

to 6.

Figure 7: AWWL score and microsaccade frequency.

Table 4 shows that there was a difference on cor-

rect rate from an effect of different AWWL scores

and experimental conditions. As shown in 2 regres-

sion lines in Figure 6, correct rate decreased as psy-

chological workload increased and correct rate was

higher in Experiment 2, where the presentation time

The Relationship between Psychological Workload and Oculomotor Indices under Visual Search Task Execution

369

Table 4: Analysis of variance table with AWWL score in

correct rate.

Factors df SS F p

AWWL 1 358.2 13.30 < 0.05

Exp. 1 602.0 22.36 < 0.05

AWWL×Exp. 1 45.0 1.67 n.s.

Residual 16 430.8

Total 19 1436.0

Table 5: Analysis of variance table with AWWL score in

MS frequency.

Factors df SS F p

AWWL 1 10.58 2.62 0.12

Exp. 1 47.97 11.90 < 0.05

AWWL×Exp. 1 0.50 0.12 n.s.

Residual 16 64.52

Total 19 123.57

was shorter. Table 5 shows that there was a signif-

icant effect in different experimental conditions on

microsaccade frequency, with p = 0.12 for AWWL

scores, indicating a trend on an effect. In other

words, microsaccade frequency was affected by dif-

ferent experimental conditions and the occurrence of

microsaccade was higher in Experiment 2, which had

a shorter presentation time. In the regression line

shown in Figure 7, microsaccade frequencydecreased

as AWWL score increased, indicating that microsac-

cade frequency was reduced as psychological work-

load increased. For pupil diameter, there was no sig-

niﬁcant effect on both AWWL score and experimen-

tal conditions, as shown in Table 6. There was no

interaction between AWWL scores and experimen-

tal conditions for all 3 indices. Thus, the effects of

different AWWL scores and experimental conditions

were found to work independently. Next, since

NASA-TLX is a macroscopic assessment, we exam-

ined the distribution of microsaccade frequency by

correct rates. As before, a plot of regression lines for

each experiment when performing an analysis of co-

Figure 8: AWWL score and pupil diameter.

Table 6: Analysis of variance table with AWWL score in

pupil diameter.

Factors df SS(10

−4

) F (10

−2

) p

AWWL 1 1.6 1.6 n.s.

Exp. 1 0.1 0.1 n.s.

AWWL×Exp. 1 6.5 6.5 n.s.

Residual 16 1607.4

Total 19 1615.6

Table 7: Analysis of variance table with microsaccade fre-

quency and correct rate.

Factors df SS F p

Correct Rate 1 8.13 2.89 n.s.

Exp. 1 44.71 15.87 < 0.05

Correct Rate × Exp. 1 0.04 0.02 n.s.

Residual 76 214.16

Total 79 267.04

Figure 9: Correct rate and microsaccade frequency.

variance at 5% level of signiﬁcance are shown in Fig-

ure 9 and the analysis of variance table is shown in

Table 7. Black colored triangles and squares repre-

sent the mean value of correct rates in Experiments 1

and 2. Table 7 shows that differences in experimental

conditions signiﬁcantly affected changes in microsac-

cade frequency and there was no interaction between

correct rates and experimental conditions. The re-

gression lines in Figure 9 shows that microsaccade

frequency was lower in Experiment 1 than in Experi-

ment 2 hence microsaccade frequencywas suppressed

in Experiment 1, which had a higher psychological

workload.

4 DISCUSSION AND SUMMARY

This article focused on microsaccade and pupil diam-

eter in 2 experiments with different presentation time

and analyzed the relationship between microsaccade

and pupil diameter using NASA-TLX, a systematic

BIOSIGNALS 2021 - 14th International Conference on Bio-inspired Systems and Signal Processing

370

measurement of psychological workload. Since there

were 80 trials per 1 subject, between-subjects factor

was taken into account by the repeated trials of sub-

jects.

• Differences between AWWL scores from NASA-

TLX assessment and experimental conditions

were found to have an effect of changing values

on 2 indices, correct rate and microsaccade fre-

quency. In other words, we could conﬁrm that

correct rate and microsaccade frequency varied

depending on the difference in conditions of 2 ex-

periments which had different presentation time.

• There were negative correlations between AWWL

scores and correct rates, AWWL scores and mi-

crosaccade frequency, positive correlation be-

tween correct rates and microsaccade frequency.

Microsaccade frequency was signiﬁcantly sup-

pressed as AWWL score increased which in-

dicates that psychological workload affects mi-

crosaccade frequency.

• From the experimental task shown in this arti-

cle, we were able to conﬁrm differences in mi-

crosaccade frequency with different degrees of

psychological workload, however no correlation

was found for pupil diameter.

• An analysis of subjective assessments made by

subjects and various oculomotor features showed

that eye movements can help to estimate psycho-

logical workload.

In the future, we would like to examine in detail

how the differences in presentation time of experi-

mental stimuli affects in the size of gaze area.

REFERENCES

Atsuhiko, I., Takeshi, K., Tohru, K., Kosuke, M., Isao, H.,

and Takehiko, B. (2011). Evaluation of stressed con-

dition using pupillary responses (japanese). Seitai Ik-

ougaku (Biomedical engineering) 49(6):946-951.

Haruki Mizushina, Kiyomi Sakamoto, H. K.(2011). The

relationship between psychological stress induced by

task workload and dynamic characteristics of saccadic

eye movements (japanese). Denshi Jouhou Tsushin

Gakkai Ronbunshi (The IEICE transactions on in-

formation and systems (Japanese edition)) Vol.j94-D

No.10 pp.1640-1651.

Hideki, F. (2010). Increased saccade error due to stress

(japanese). Roudou Anzen Eisei Sougou Kenkyujo

Tokubetu Kenkyu Houkoku (National Institute of Oc-

cupational Safety and Health, Japan Report).

Hiroyuki, S. (2010). Temporal changes in the frequency

of microsaccades during the visual angle search task

(japanese). VISION Vol.22, No.2, 131-134.

Iijima, A. (2012). Visually induced autonomic modulation

and evaluation of the autonomic nervous system with

visual function (japanese). Equilibrium Res Vol.71(3)’

194-199.

Keiichiro, I. and Shiro, U. (2012). Neuronal mechanisms

for generation of microsaccades (japanese). Nihon

Shinkei Kairo Gakkaishi (Japanese Neural Network

Society report) Vol.19, No.3’135-144.

Krzysztof, K., Andrew, T., Anna, N., Cezary, B., and

Izabela, K. (2018). Eye tracking cognitive load

using pupil diameter and microsaccades with ﬁxed

gaze. Eye tracking cognitive load using pupil diameter

and microsaccades with ﬁxed gaze.PLoS ONE 13(9):

e0203629.

Ralf, E. (2006). Microsaccades: a microcosm for research

on oculomotor control, attention, and visual percep-

tion. CHAPTER 9, Martinez-Conde, Macknik, Mar-

tinez, Alonso and Tse(Eds.) Progress in Brain Re-

search, Vol.154.

Ralf, E., Petra, S., Konstantin, M., and Hans, T. (2015).

Microsaccade toolbox 0.9. Potsdam Mind Research

Repository.

Ralf, E. and Reinhold, K. (2003). Microsaccades uncover

the orientation of covert attention. Vision Research,

43, 1035-1045.

Shigeru, H. and Naoki, M. (1996). Japanese version of

nasa task load index: Sensitivity of its workload

score to difﬁculty of three different laboratory tasks

(japanese). Ningen Kougaku (The Japanese journal of

ergonomics) 32(2), 71-79.

Shinji, M. (2015). Special issues no. 3:measurement tech-

nique for ergonomics, section 3:psychological mea-

surements and analyses(6), mental workload assess-

ment and analysis -a reconsideration of the nasa-tlx-

(japanese). Ningen Kougaku (The Japanese journal of

ergonomics) Vol51, No.6.

Shinji Miyake, M. K.-S. (1993). Subjective mental work-

load assessment technique-an introduction to nasa- tlx

and swat and a proposal of simple scoring methods-

(japanese). Ningen Kougaku (The Japanese journal of

ergonomics) Vol29, No.6.

Yuta, T., Atsushi, N., and Nishida, T. (2015). Quanti-

tative relationship between human internal state and

pupil diameter (japanese). Jouhou Shori Gakkai

Dai77kai Zenkokutaikai (Information Processing So-

ciety of Japan 77th National Convention), 4-413 4-

414.

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