Visual Perception, Binocular Rivalry, and Fatigue-Related Individual Differences in Colour and Illumination Judgement

Characterising Individual Differences in Colour Perception and Binocular Rivalry and Their Associations With Chronotype, Sex, and Sleep

This observational study aims to characterise individual differences in colour perception and binocular rivalry. Participants will complete computer-based visual perception tasks, including a colour perception task and a binocular rivalry task. The study will first examine whether individuals show measurable differences in these perceptual responses. It will then explore whether these differences are associated with chronotype, sex, sleep-related measures, and subjective fatigue. The findings may help clarify how stable individual characteristics and daily physiological states relate to visual perception.

Study Overview

• Status: Not yet recruiting
• Conditions: Color Perception; Colour Perception; Binocular Rivalry
• Intervention / Treatment: Other: Computer-Based Visual Perception Tasks

Detailed Description

Colour perception and binocular rivalry both show variability across individuals. However, the extent to which these individual differences are stable and whether they are associated with personal or physiological factors remains unclear. This study will use behavioural visual perception tasks to measure individual differences in colour perception and binocular rivalry. Participants will complete a colour perception task and a binocular rivalry task, along with questionnaire measures related to chronotype, sleep, fatigue, and demographic characteristics including sex.

The primary aim is to determine whether measurable individual differences are present in colour perception and binocular rivalry performance. The secondary aim is to examine whether these differences are associated with chronotype, sex, sleep-related variables, and subjective fatigue. The study is observational and does not involve a clinical intervention, drug, biologic product, or medical device.

• Study Type: Observational
• Enrollment (Estimated): 128

Contacts and Locations

• Study Contact: Name: Cehao Yu, PhD; Phone Number: +852 3400 3012; Email: cehao.yu@polyu.edu.hk
• Study Contact Backup: Name: Junkai Che, Master; Phone Number: +852 9783 8643; Email: junkai.che@connect.polyu.hk

Study Locations

• Hong Kong
  • Kowloon
    • Hung Hom, Kowloon, Hong Kong
      • The Hong Kong Polytechnic University, Department of Applied Social Sciences
      • Contact: Cehao Yu, PhD; Phone Number: +852 3400 3012; Email: cehao.yu@polyu.edu.hk
      • Contact: Junkai Che, Master; Phone Number: +852 9783 8643; Email: junkai.che@connect.polyu.hk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Healthy adult volunteers will be recruited from the university community and/or the surrounding community. Participants will complete computer-based colour perception and binocular rivalry tasks, together with self-report measures of chronotype, sleep, fatigue, and demographic characteristics.

Description

Inclusion Criteria:

• Adults aged 18 years or older.
• Normal or corrected-to-normal visual acuity.
• Normal or corrected-to-normal binocular vision.
• Normal colour vision, or no self-reported colour vision deficiency.
• Able to understand the study instructions and provide informed consent.
• Able to complete computer-based visual perception tasks and self-report questionnaires.

Exclusion Criteria:

• Self-reported colour vision deficiency.
• Uncorrected visual impairment or eye conditions that may interfere with visual perception tasks.
• Strabismus, amblyopia, or other binocular vision problems that may interfere with binocular rivalry testing.
• History of neurological disorders, photosensitive epilepsy, or severe sensitivity to flickering visual stimuli.
• Current condition or medication that, in the investigator's judgment, may substantially affect visual perception, attention, or task performance.
• Inability to complete the task procedures or provide valid responses.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Healthy Adult Participants; Healthy adult volunteers aged 18 to 25 years with normal or corrected-to-normal visual acuity and normal colour vision, recruited from the university and surrounding community. In a single laboratory session, participants complete computer-based colour perception and binocular rivalry tasks and self-report questionnaires on chronotype, sleep, fatigue, and demographic characteristics.

Other: Computer-Based Visual Perception Tasks; Participants will complete computer-based visual perception tasks, including a colour perception task and a binocular rivalry task. These tasks are used to measure individual differences in perceptual responses and are not intended as a clinical intervention.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mean colour-adjustment values on the colour perception task	Colour perception will be measured using a computer-based colour adjustment task. Participants will adjust the appearance of a target object or stimulus, and outcome variables will include adjustment values in colour space, such as chromaticity, hue, saturation, or luminance-related measures, depending on the final task implementation. These measures will be used to characterise individual differences in colour perception.	Day 1 (single laboratory session)
Mean perceptual dominance duration during binocular rivalry	Binocular rivalry is measured with a computer-based dichoptic task in which a different image is presented to each eye. Perceptual dominance duration is the mean length of time, in seconds, that one stimulus remains exclusively visible before perception switches to the other. Longer mean durations indicate more stable, slower-switching rivalry.	Day 1 (single laboratory session)
Mean alternation rate during binocular rivalry	Binocular rivalry is measured with the same computer-based dichoptic task. Alternation rate is the mean number of perceptual switches between the two stimuli per minute of viewing. Higher alternation rates indicate faster perceptual switching between the two eyes' images.	Day 1 (single laboratory session)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Morningness-Eveningness Questionnaire (MEQ) score	Chronotype assessed using the Morningness-Eveningness Questionnaire (MEQ). Total scores range from 16 to 86; higher scores indicate greater morningness (a stronger morning-type preference) and lower scores indicate greater eveningness.	Day 1 (single laboratory session)
Pittsburgh Sleep Quality Index (PSQI) global score	Sleep quality assessed using the Pittsburgh Sleep Quality Index (PSQI). The global score is the sum of seven component scores and ranges from 0 to 21; higher scores indicate worse sleep quality (a global score above 5 indicates poor sleep quality).	Administered once, within 7 days before or at the single laboratory session (Day 1); the PSQI assesses sleep over the preceding 1 month.
Karolinska Sleepiness Scale (KSS) score	Subjective sleepiness/fatigue assessed using the Karolinska Sleepiness Scale (KSS), a single-item 9-point scale. Scores range from 1 to 9; higher scores indicate greater sleepiness. The pre-task to post-task change in KSS score may also be reported.	Day 1: assessed immediately before and immediately after the visual perception tasks, which are completed within a single session lasting up to approximately 1 hour.

Collaborators and Investigators

• Sponsor: The Hong Kong Polytechnic University
• Investigators: Principal Investigator: Cehao Yu, PhD, The Hong Kong Polytechnic University

Publications and helpful links

General Publications

• Yang E, Blake R, McDonald JE 2nd. A new interocular suppression technique for measuring sensory eye dominance. Invest Ophthalmol Vis Sci. 2010 Jan;51(1):588-93. doi: 10.1167/iovs.08-3076. Epub 2009 Jul 23.
• Webster MA, Miyahara E, Malkoc G, Raker VE. Variations in normal color vision. II. Unique hues. J Opt Soc Am A Opt Image Sci Vis. 2000 Sep;17(9):1545-55. doi: 10.1364/josaa.17.001545.
• Foster DH. Color constancy. Vision Res. 2011 Apr 13;51(7):674-700. doi: 10.1016/j.visres.2010.09.006. Epub 2010 Sep 16.
• Wallisch P. Illumination assumptions account for individual differences in the perceptual interpretation of a profoundly ambiguous stimulus in the color domain: "The dress". J Vis. 2017 Apr 1;17(4):5. doi: 10.1167/17.4.5.
• Gegenfurtner KR, Bloj M, Toscani M. The many colours of 'the dress'. Curr Biol. 2015 Jun 29;25(13):R543-4. doi: 10.1016/j.cub.2015.04.043. Epub 2015 May 14.
• Lafer-Sousa R, Hermann KL, Conway BR. Striking individual differences in color perception uncovered by 'the dress' photograph. Curr Biol. 2015 Jun 29;25(13):R545-6. doi: 10.1016/j.cub.2015.04.053. Epub 2015 May 14.
• Toscani M, Gegenfurtner KR, Doerschner K. Differences in illumination estimation in #thedress. J Vis. 2017 Jan 1;17(1):22. doi: 10.1167/17.1.22.

Study record dates

Study Major Dates

• Study Start (Estimated): July 1, 2026
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: June 22, 2026
• First Submitted That Met QC Criteria: June 22, 2026
• First Posted (Actual): June 26, 2026

Study Record Updates

• Last Update Posted (Actual): July 6, 2026
• Last Update Submitted That Met QC Criteria: July 1, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Sleep; Chronotype; Visual perception; Sex differences; Individual differences; Colour perception; Color perception; Binocular rivalry; Subjective fatigue
• Other Study ID Numbers: HSEARS20260621001 (Other Identifier: The Hong Kong Polytechnic University)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No