Pupil dilation but not microsaccade rate robustly reveals decision formation

Area of Science:

• Cognitive Neuroscience
• Psychology

Background:

• Pupil dilation is a physiological indicator of arousal.
• It is generally considered unspecific but can reflect cognitive processes like decision formation.

Purpose of the Study:

• To investigate if pupil dilation can predict choice in a Go/NoGo task.
• To explore the utility of pupil dilation and microsaccades in decision research.
• To differentiate decision-related pupil signals from interfering factors.

Main Methods:

• A Go/NoGo task involving letter selection.
• Measurement of pupil dilation and microsaccade rate.
• Analysis of pupillary signals under varying conditions (brightness, motor execution).

Main Results:

• Choice was robustly predicted by pupil dilation, even with interfering factors.
• A larger difference in pupil dilation between target and distractor for NoGo trials compared to Go trials was observed.
• Decision formation was primarily observed in pupil diameter, while microsaccades reflected motor execution and choice post-key press with a smaller effect size.

Conclusions:

• Pupil dilation is a valuable, specific indicator of decision formation.
• Combining pupil dilation and microsaccade analysis can help dissociate cognitive signals from confounding variables.
• Findings suggest a selective role for the locus coeruleus over the superior colliculus in decision formation.