Further progress towards disambiguating the effects of cognitive load and light on pupil diameter

In driving simulator studies participants complete both visual and aural task. The most obvious visual task is driving itself, but there are others such as viewing an LCD screen that displays a map. Aural tasks include talking to an in-vehicle computer. I am very interested in estimating the cognitive load of these various tasks. One way to estimate this cognitive load is through changes in pupil diameter: in an effect called the Task Evoked Pupillary Response (TEPR) [1], the pupil dilates with increased cognitive load.

However, in driving simulator studies participants scan a non-uniformly illuminated visual scene. If unaccounted for, this non-uniformity in illumination might introduce an error in our estimate of the TEPR. Oskar Palinko and I will have a paper at ETRA 2012 [2] extending our previous work [3], in which we established that it is possible to separate the pupil’s light reflex from the TEPR. While in our previous work TEPR was the result of participants’ engagement in an aural task, in our latest experiment TEPR is due to engagement in a visual task.

The two experiments taken together support our main hypothesis that it is possible to disambiguate (and not just separate) the two effects even in complicated environments, such as a driving simulator. We are currently designing further experiments to test this hypothesis.


[1] Jackson Beatty, “Task-Evoked Pupillary Responses, Processing Load, and the Structure of Processing Resources,” Psychological Bulletin, 276-292, 91(2)

[2] Oskar Palinko, Andrew L. Kun, “Exploring the Effects of Visual Cognitive Load and Illumination on Pupil Diameter in Driving Simulators,” to appear at ETRA 2012

[3] Oskar Palinko, Andrew L. Kun, “Exploring the Influence of Light and Cognitive Load on Pupil Diameter in Driving Simulator Studies,” Driving Assessment 2011