Pupillary Light Response in Gaze Cueing
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In this paper we show that the pupillary light response reflects covert shifts of attention when a gaze cue is used. Participants fixated on the center of a display that had a gray background and two circles, one black (dark) and one white (bright), on which the target appeared. The pupil initially constricted when gaze cued attention covertly to the bright, relative to the dark, area indicating that the attention was indeed cued to this side. Our results suggests that gaze is the best attentional facilitator, compared to an exogenous or endogenous cue. It also suggests that a gaze cue does not fall in the domain of only an endogenous or exogenous cue, but incorporates features from both and is therefore different from any other attentional facilitator. We conclude that the pupillary light response can be elicited with a covert gaze cue and that the pupillary light response is a complex eye movement that reflects if and where we pay attention to.