Personality Test based on Eye Tracking Techniques

Yun Zhang The School of Electronic and Information Engineering

Xi’an Jiaotong University Xi’an, China

zhangyun2011@xjtu.edu.cn

Wei Xin, Danmin Miao Department of Psychology

The Fourth Military Medical University Xi’an, China psych@fmmu.edu.cn

Abstract—this paper presents an original research on eye tracking based personality test. To deal with the unavoidable human deception and inaccurate self-assessment during subjective psychological test, eye tracking techniques are utilized to reveal the participant’s cognitive procedure during test. A non-intrusive real-time eye tracking based questionnaire system is developed for Chinese military recruitment personality test. A pilot study is carried out on 12 qualified samples. The preliminary result of experiment indicates a strong correlation between the participant’s fixation features and test results. And such kind of relationship can be developed as an assistive indicator or a predictive parameter to traditional psychological test result to highly improve its reliability and validity in future applications.

Keywords—personality test; eye tracking techniques; psychometry; prediction study; fixations, eye tracking metrics.

I. INTRODUCTION Personality is the combination of behavior, emotion,

motivation, and thought patterns that define an individual. A personality test is questionnaire or other standardized instrument designed to reveal aspects of an individual's character by psychological scale study[1]. Personality tests are used in a wide range of contexts, such as individual and relationship counseling, career counseling, employment testing, occupational health and safety and customer interaction management ,etc. which is estimated to be worth more than $4 billion a year in industry[2].

However, one of the biggest disadvantages of existing personality test is that it is possible for people to engage in deception when answering questions. Even though techniques can be used to detect deception, people can still successfully provide false answers often in an effort to "fake good" or appear more socially acceptable and desirable. Another potential problem is that people are not always good at accurately describing their own behavior. People tend to overestimate certain tendencies while underestimating other characteristics. This can have a serious impact on the accuracy of a personality test[3].

Eye-tracking is a technology that allows for the recording of eye gaze positions and eye movements when looking to texts, images, displays, or moving scenes. It opens a window and acts as a special tool to both qualitatively and quantitatively measure the untouchable human consciousness and behavior, which has caught great interests of scientists

from different areas and interdisciplinary subjects, such as neuroscience and cognition and psychology, industrial engineering, commercial marketing, computer science and etc.[4]

As a result, the objective of the research in this paper is to use eye tracking technique to observe the people’s cognitive behavior during the self-report test. By further analysis of the correlation between the personality test result and the corresponding eye movements, the study aim to firstly discover whether there is any insight between the personal eye tracking metrics and their answers. Furthermore, the study is to use the participant’s gaze data as a reference to his personality test result to substantially improve the traditional psychological scale’s reliability and validity by means of objective real-time biodata response.

The rest of the paper is structured as follows. Section 2 describes the development of personality test and one of application on Chinese military recruitment questionnaire system, and also discuss the theory and application of eye tracking techniques .Section 3 introduces a practical eye tracking based personality test system for military recruitment. The experiment setup of pilot study is discussed. In section 4 , the experiment result and discussion are developed. It has shown a strong correlation between the fixation features vectors and the test results. And such kind of relationship can be utilized to predict the personality test by multidimensional scaling. Finally, section 5 concludes the paper and deploy the further research work in future.

II. BACKGROUND

A. The Development of Personality Test and Chinese Soldier Personality Questionnaire The first personality tests were developed in the 1920s [5]

and were intended to ease the process of personnel selection, particularly in the armed forces. Because of these early efforts, a wide variety of personality tests have been developed, notably the Myers Briggs Type Indicator (MBTI)[6], The Minnesota Multiphasic Personality Inventory (MMPI), and a number of tests based on the Five Factor Model of personality, such as the Revised NEO Personality Inventory. Among them, the MMPI is the most widely used and researched standardized psychometric test of adult personality and psychopathology.[7]

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2015 International Conference on Affective Computing and Intelligent Interaction (ACII)

TABLE I. THE 11 DIMENSION OF CASPQ QUESTIONARE

The original MMPI, first published by the University of Minnesota Press in 1943, and then update to the MMPI-2 in 1989, MMPI-A in 1992, and MMPI-2-RF in 2008 finally. Psychologists and other mental health professionals use various versions of the MMPI to develop treatment plans; assist with differential diagnosis; help answer legal questions (forensic psychology); screen job candidates during the personnel selection process; or as part of a therapeutic assessment procedure.

One of the very practical application of personality assessment world widely is on military recruitment to ensure the qualified solider candidates. In China, the psychology department of the Fourth Military Medical University developed The Chinese Army Servicer Personality Questionnaire (CASPQ) in 2006 to do the psychological selection for Chinese recruit candidates[8][9]. Mainly based on MMPI, CASPQ include 11 dimensions psychological scales, which are listed in the following table I. There are altogether 309 items in CASPQ, the first three dimensions belong to validity scales and the rest eight dimensions belong to clinical scales.

Finally, Like many standardized tests, scores on the various scales of the CASPQ are not representative of either percentile rank or how "well" or "poorly" someone has done on the test. Rather, analysis looks at relative elevation of factors compared to the various norm groups studied. Raw scores on the scales are transformed into a standardized metric known as T-scores

(Mean or Average equals 50, Standard Deviation equals 10), making interpretation easier for soldier recruitment.

B. Eye Tracking Techniques Eye tracking techniques aim to precisely and non-

intrusively trace the point of gaze of human being. It has long been known and used as a method to study the visual attention of individuals. There are several different techniques to detect and track the movements of the eyes. However, when it comes to remote, non-intrusive, eye tracking the most commonly used technique is Pupil Centre Corneal Reflection (PCCR). The basic concept is to use a light source to illuminate the eye causing highly visible reflections, and a camera to capture an image of the eye showing these reflections. The image captured by the camera is then used to identify the reflection of the light source on the cornea (glint) and in the pupil. As illustrated in Fig. 1, a light source is used to cause reflection patterns on the cornea and pupil of the test person. A camera will then be used to capture an image of the eye. The direction of the gaze is then calculated using the angles and distances[11].

We are then able to calculate a vector formed by the angle between the cornea and pupil reflections – the direction of this vector, combined with other geometrical features of the reflections, will then be used to calculate the gaze direction. Usually, near infrared illumination is used to create the reflection patterns on the cornea and pupil of the eye of a user and two image sensors are used to capture images of the eyes and the reflection patterns. Advanced image processing algorithms and a physiological 3D model of the eye are then used to estimate the position of the eye in space and the point of gaze with high accuracy.

Eye tracking analysis is based on the important assumption that there is a relationship between fixations, our gaze and what we are thinking about. Therefore, it is an important technique that offers an objective way to see where in a scene a person’s visual attention is located. On the one hand, it can be widely

applied on neuroscience , psychology ,reading research, scene perception, visual search, information processing, industrial

engineering and marketing , aviation, driving, visual inspection, marketing, advertising, computer science, etc. On

the other hand, it is necessary to have a clear methodology that is adequate to the context and objectives of the study if we

wish to understand and interpret the eye tracking data correctly.

Fig. 1. Pupil Centre Corneal Reflection technique (PCCR)

No. Abbreviation Description What is measured No. of

items

1 LS Lie Client "faking good"

15

2 KS Defensiveness Denial/Evasiveness 29

3 FS Infrequency Client "faking bad" (in first half of test)

59

4 HPS Hypochondriasis

Concern with bodily symptoms

32

5 DEP Depression Depressive Symptoms

57

6 HYS Hysteria Awareness of problems and vulnerabilities

59

7 PSD Psychopathic Deviate

Conflict, struggle, anger, respect for

society's rules 47

8 MAI Hypomania Level of excitability

46

9 PAR Paranoia Level of trust,

suspiciousness, sensitivity

40

10 PST Psychasthenia

Worry, Anxiety, tension, doubts, obsessiveness

48

11 SCH Schizophrenia

Odd thinking and social alienation

75

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Fig. 2. The setup of eye tracking based personal

III. METHOD

A. The Setup of Eye Tracking Based PersonaPlatform The platform of eye tracking based pe

presented in Fig.2. To non-intrusively colleceye movement of participants during the test, integrated with the questionnaire system. calibration between the individual’s and the 2the platform carries out the psychological tethe eye movement data simultaneously. Finadata are collected for further analysis ofbetween the test result and participants cognicorresponding eye movement metrics.

B. Experiment A preliminary experiment of 14 participant

in the eye tracking lab of Xi’an Jiaotong participants are between the ages of 19-30 yewere male, 2 female. To ensure the validity oand the diversity of the test result, we recruit non-military University who have never bCASPQ before , while another 6 graduatemilitary University who have already succeCASPQ and are familiar with the rules anpsychological assessment. The actualenvironment is demonstrated in Fig. 3

Fig. 3. The actual eye tracking-based CASPQ experi

ity test platform

lity Test

ersonality test is cted the real time the eye tracker is After necessary

2D display plane, est while collects ally , all the gaze f the correlation itive process and

ts was carried out University. The

ears, of which 12 of the experiment 6 freshmen from

been exposed to ed students from essfully pass the nd form of such l experimental

imental environment

Fig. 4. The interface and one of

Fig. 5. Experiment p

The experiment utilizes Tobii TXCASPQ with a 60 Hz sampling ratethe CASPQ item are shown in Fig.4items in CASPQ which are all “YesFor each item there is a time controrecord and adjust the participantexperiment, each participant need toto ensure the reliability of the experi

The experiment procedure is prstep is to do the preparation, participant’s individual informationconsent and experiment descdependableness and successfulnesssecond step is to adjust the participabest eye movement data. The thitracking experiment calibration toquality of all the gaze data. Finally,

IV. RESULT AND DI

A. The CASPQ Result of the Pilot SThe 12 effective participants’ CA

distributions on 11 dimensions of t

Preparation • Record the participant

variables• Show the informed consent

• Show the experiment description

Experiment start

f test item of CASPQ

procedure

X 300 eye tracker to present e. The interface and one of 4. There are altogether 309 ” or “No” choice questions. lling bar on the interface to s answering time. Before o sign the informed consent iment data.

resented in Fig.5. The first including recording the

n and showing the informed cription to ensure the s of the experiments. The ant’s situation to acquire the ird step is to do the eye

o ensure the accuracy and start the experiment.

ISCUSSION

Study ASPQ result and their score the pilot study as shown in

Adjust•Adjust the participant sitting position and eyes direction to best fit the

eye tracker

Calibration•Double eyes nine

points calibration

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table 2. The first row from top is the subjectsCASPQ result, and all the 11 dimension explai

Consequently, each row stands for otraditional CASPQ evaluation. The second cothe result of the psychological score for rstands for psychological qualified soldier , whiB. The Correlation between Participant’s Fix

Distrubution and Corresponding CASPQ R Among all the other eye tracking met

usually the most import and the very first to stugaze data. The definition of fixation or visuahuman ability to maintaining of the visual glocation (as shown in Fig.6 ). Generally, Thevaries from about 100 to 600 milliseconds, dubrain starts to process the visual information reyes. All the information from the scene is during fixations whose typical frequency is < 3

Based on the eye movement data of the 1the pilot study, we firstly focus on the fixaqualified soldier (Type “A” in table II) and (Type “C” in table II). As suggested in tabparticipants are named as: No.1 to No.12, anumber is from 1 to 309, so we get the statisticthe pilot

Fig. 6. The fixation of qualified (green dots) and unquadots) participants on item No 155

TABLE II. THE CASPQ RESUSub Result LS KS FS

01 A 37 59.5 33.

02 A 44.3 43.7 58.

03 A 40.7 50.5 41.

04 A 33.4 43.7 46.

05 A 51.6 59.5 38.

06 A 40.7 57.2 41.

07 C 44.3 36.9 63.

08 C 40.7 43.7 58.

09 C 40.7 32.4 56.

10 A 48 55 46.

11 A 33.4 55 51.

12 A 37 48.2 41.

s number (Sub.) , ined in table 1.

one participant’s lumn from left is recruitment. “A” ile “C” stands for

high possibility of schizoid personafurther psychological interview discriminate. In the pilot study , thesamples account for 25% , whicrepresentativeness for in-depth investigation.

xation Result. trics, fixation is udy from the raw al fixation is the gaze on a single e fixation lengths uring this stop the received from the mainly acquired

3Hz.

2 participants on ation features of unqualified ones

ble III, let the 12 and the test item cs of fixations on

study.

alified (blue and red

As a result, the fixation numbevector of 309 dimension. Then

experiment can be illustrated aBecause of the inevitable errors experiment, there are 19 items lost number of participant No.1. Therexclude all the “missing number” oget the 269 dimension fixation vecvisualization of their correlation isright side color bar to visualize thematrix between participants. The nuand the bottom row stands for 1~12stands for the coefficient of correlatblue color stands for coefficient of cabsolute value here).For example , ais red. This is because the diagocoefficient of fixation vector belongwhich defiantly equals to “1”.

TABLE III. THE STATISTICS OF EACH PPLOT STUDY

ULT AND 11 DIMENSION SCORE DISTRIBUTION OF THE PILOT SHPS DEP HYS PSD MAI P

7 48.1 40.6 62.8 46.9 50.4 5

7 57.1 53.2 50.1 66.6 67.9 4

2 39.2 40.6 50.1 44 65.4 4

2 48.1 65.8 52.6 61 28 5

7 45.1 48.2 60.2 52.5 25.5 4

2 48.1 55.7 55.2 58.2 40.5 4

7 66.1 70.9 65.3 44 45.4 6

7 63.1 73.4 67.8 46.9 40.5 7

2 72.1 75.9 60.2 66.6 43 7

2 66.1 55.7 57.7 58.2 50.4 5

2 51.1 53.2 50.1 46.9 57.9 4

2 45.1 35.5 50.1 58.2 45.4 2

No1 No2 No3 No4 No5 No6 No7 1 5 5 7 11 8 9 30 2 4 6 6 5 4 5 5 3 3 6 3 6 6 4 13 4 12 14 7 7 9 13 16 5 5 14 10 10 5 7 8 6 4 4 4 5 4 5 6 7 5 12 7 5 6 8 19

… … … … … … … … … … … … … … … … 308 5 14 8 7 5 8 11 309 4 6 3 8 5 10 12

ality deviations, which need with clinical doctor to

ere are 3 “C” among all the ch keep the diversity and

eye movement data

er of each participants is a the fixation set of the

as { }, 1, 2,3,...,12iF i ∈.

during the eye tracking the corresponding fixation

refore, the first step is to on the database. Finally, we ctor of 12 participants. The s demonstrate in Fig.7.The e relationship of correlation umber along the left column 2 participants. The red color tion equals to “1”, while the correlation equals to “0” (all all the color on the diagonal nal line is the correlation

gs to participants themselves,

PARTICIPANTS; FIXATION ON THE Y

STUDY

PAR PST SCH

52.9 41 39.5

49.6 69.6 56.9

46.4 41 35.8

56.2 53 49.4

46.4 38 37

49.6 42.5 39.5

66.1 71.1 77.9

72.6 77.2 63.1

75.9 81.7 69.3

52.9 56.1 51.9

49.6 50 48.2

29.9 53 51.9

No8 No9 No10 No11 No1219 18 16 9 8

5 5 10 3 47 10 9 4 38 12 11 6 58 6 3 1 36 5 3 5 2

17 9 14 7 4… … … … … … … … … …

11 8 9 4 513 8 19 3 4

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Fig. 7. The correlation between 12 participants fixation vector on the CASPQ

From Fig.7, we can obviously find that the correlation coefficient colors of No.7 and No.8 are distinctively different from others. (marked with a horizontal and vertical red frame in Fig.7) .Such significances are happened to be consisted with traditional CASPQ results, in which No.7 and No.8 are unqualified soldier candidates with the results as Type “C” (as shown in table II). Accordingly, we infer that the fixation feature of participant during personality test can be used as an objective biodata to predict the test result.

C. Predict the Personality Test Reslut by Multidimensional Scaling Distance To take into account all of the temporal-spatial fixation

distribution features of the participants, we summarized the data using multidimensional scaling (MDS). With the 269 × 12 fixation matrix (table III), we applied MDS (Kruskal & Wish 1978) to reduce the fixation vector’s dimension to a 3D space to separate the qualified soldier candidates from the unqualified ones. The extracted 3 dimension fixation vector features are listed in table IV.

Then we plot those participants in a 3D space to explore the relative relationship between the qualified soldier and unqualified soldier by means of fixation features during CASPQ. In Fig.8(a), the three coordinate axes stands for the fixation features (X1,X2,X3) ,the red dots are the participants of unqualified soldier candidates (No. 7, No.8 and No.9 in table IV), while the blue dots are the qualified ones. From the distribution of the fixation features of the two groups of participants, it is very clear to use any liner or non-liner discriminant method to divide them. For example, the participants in the pilot study can be divided by a 2D plane by means of Fisher Liner Discriminant (FLD), as shown in Fig.8(b) and Fig.8(c).

TABLE IV. THE FIXATION FEATURES OF 12 PARTICIPANTS BY MDS (DIMENSION=3)

Feature Sub. X1 X2 X3 CASPQ

result No1 1.5722 -0.2952 -0.4551 √ No2 0.2291 -0.0997 -0.7786 √ No3 -0.0928 0.1323 -0.0409 √ No4 0.5261 -0.1018 -0.0397 √ No5 0.9484 -0.0527 -0.0057 √ No6 -1.1013 0.034 -0.5988 √ No7 -3.5572 0.829 -0.4811 ×No8 1.0243 0.9841 0.0423 ×No9 -1.5609 0.0089 0.6912 ×No10 -0.7885 -1.8145 0.3972 √ No11 0.5726 0.257 1.3484 √ No12 2.228 0.1187 -0.0791 √

Fig. 8. The fixation features for predict personality test (a)The fixation features of qualified soldier candidates (blue dots ) and unqualified soldier (red dots) candidates by MDS analysis (b) the top view of FLD plane for the two groups of participants (c) the bottom view of FLD plane for the two groups of participants

(a)

(b)

(c)

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V. CONCLUSION AND FUTURE WORK In this paper, we carried out a research of eye-tracking

based personality test in order to utilize the objective biofeedback to improve the validity and reliability of traditional self-report based psychological test. This is a totally original interdisciplinary study between psychology, visual cognition and human emotion which has not been report on any paper before.

The study is the collaboration with the psychology department of Fourth Military Medical University which have over ten years researching work experiences on Chinese military psychological scale assessments. Moreover our research can be tested on a very large sample population during recruitment each year, which provide very valuable database for verification and further study.

Based on the highly promising experiment result in the pilot study in this paper, our research prepare to conduct with much more sample to setup an eye tracking based personality test database, which will involve hundreds people to attend. On the other hand, only one eye tracking metrics, although very important, is involved in this paper. In the next step of the study, more eye tracking metrics will be investigated, such as saccade, scan path, and fixation backwards, etc.

In the future, the personality test is no longer a subjective process but combined with non-intrusive objective method. At that time, the participant’s deception and inaccurate self-assessment is not problems any more. The eye tracking techniques may essentially change the form of personality test by concerning not only about the participant’s self-report results but also about their cognitive procedures, which is both qualitative and quantitative assessment.

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