I wish to measure the pupil diameter of eyes when subjects are performing various tasks on computer, and since I'm new to the eye-tracking field, I hope to know more about the factors I need to control when designing these experiments.
I know environment luminance level need to be controlled. Right now I think I should adjust the luminance in the room to make sure each subject's pupil diameter is at moderate level, but are there any thing more to be considered?
I have also heard about that the average computer screen brightness should be the same throughout the task, is this correct?
And are there any books/articles talking about these issues when designing the experiment?
Thanks!
In my opinion the main factor is to maintain the same environment luminance level during your experiment.
Good Luck !
Yes, the average computer screen brightness should also be constant since the pupils will adapt to this.
What is the task? I think ist easy to keep the screen brightness at the same level if ist only some black text against some background, but if you have e.g pictures or videos it becomes difficult. Then, you should know how bright the screen was during a task to compare between different tasks.
Also other factors can influence pupil Diameter, like droug intake or sleep levels, possibly also certain illnesses.
Kind regards,
Patrick
In addition to the factors above (retinal illumination, drugs, etc)
other factors known to have an influence on pupil size include:
a) age (see e.g. Winn, B., Whitaker, D., Elliott, D. B., & Phillips, N. J. (1994). Factors affecting light-adapted pupil size in normal human subjects. Investigative Ophthalmology & Visual Science, 35(3), 1132-1137.)
b) accommodation (classic near triad response)
c) cognitive load (e.g. Knapen, T., de Gee, J. W., Brascamp, J., Nuiten, S., Hoppenbrouwers, S., & Theeuwes, J. (2016). Cognitive and ocular factors jointly determine pupil responses under equiluminance. PloS one, 11(5), e0155574.; https://pdfs.semanticscholar.org/8ce8/bc159ac21268638f6660488af883e0fe5310.pdf)
It is necessary to find a baseline before you eventual present stimuli. https://peerj.com/preprints/2725/
Kindly go through Pupillary diameter assessment: need for a graded scale.
Litvan I, et al. Neurology. 2000. And https://www.researchgate.net/publication/288199062_Reliability_of_pupillary_diameter_assessment#rft
Monitoring and Processing of the Pupil Diameter Signal for Affective Assessment of a Computer User by Ying Gao et Al is another study you should look at.
The factors that you should control is age and sex matched subjects, equal background and computer luminance, similar quantifiable tasks, not on any kind of drug, intoxicant or even tea/coffee. The amount of sleep had, the activity levels, subject refractive status, presence or absence of dry eye and computer vision syndrome. A lot of factors I know but making sure these are addressed will give you high quality data.
If you are using a remote eye-tracker (i.e., not head mounted) don't forget to control for the distance between the eye tracker and the head/eyes.
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