Exploring the interaction between the pupillary light response after exogenous attentional cueing and detection performance

Abstract

Pupil size changes under different light conditions. Whereas this pupillary light response (PLR) has long been regarded to be influenced by luminance only, recent studies indicated the PLR is also modulated by cognitive factors such as the allocation of spatial attention. This attentional modulation of the PLR has previously been hypothesized to facilitate detection and discrimination of visual information. Here, we replicated the finding that the pupil dilates when a cue is presented at the dark side of a screen and constricts when the cue is presented at the bright side, even when the eyes are fixated at the center. Furthermore, we investigated whether this modulation of the PLR, evoked by exogenous shifts of covert attention, facilitates perception operationalized as detection performance for threshold stimuli. Results showed that a larger pupil was indeed related to increased detection performance, although this effect was restricted to conditions in which both cue and target appeared on a dark surface. Our findings are in line with the notion that pupil dilations improve detectability, whereas pupil constrictions enhance discriminability of small stimuli.