Pupil Dilation Reflects Task Relevance Prior to Search

Area of Science:

• Cognitive Neuroscience
• Visual Perception

Background:

• Visual working memory (VWM) holds task-relevant object representations (templates) to guide attention during visual search.
• The pupil response is a physiological measure sensitive to cognitive processes, but its use in differentiating template-matching stimuli is underexplored.

Purpose of the Study:

• To investigate if pupil responses can distinguish between stimuli matching a task-relevant template and irrelevant stimuli before visual search.
• To explore the pupil response as a potential neural signature of template activation in VWM.

Main Methods:

• Two experiments involved observers memorizing a target color (template) for a visual search task.
• A colored probe stimulus was presented before the search display, and pupil size was measured.
• The probe stimulus could match the relevant template, an irrelevant color, or be a novel color.

Main Results:

• Significantly smaller pupil size was observed for probe stimuli matching the search template compared to irrelevant colors (Experiment 1).
• This template-matching effect was replicated, and repetition priming was ruled out as the sole cause (Experiment 2).

Conclusions:

• The pupil response selectively reflects the task-relevant template held in visual working memory.
• Pupilometry offers a non-invasive method to infer cognitive states related to visual search and attention.