Abstract
The ability to make saccade is necessary for exogenous spatial attention (Smith & Schenk, 2012), but its necessity for endogenous attention is not well known. We investigated whether endogenous space- and feature- based attention can operate at a location out of the range for saccades. We used an abduction procedure with monocular viewing to manipulate saccadic range. In normal sitting position, both nasal and temporal visual fields were within the saccadic range. During abduction, participants sat in a rotated position (25°) while fixating the screen center, such that the temporal visual field was outside the saccadic range. Importantly, stimuli were presented at identical retinal locations in both normal and rotated positions. In Experiment 1, we manipulated spatial attention by instructing participants to attend to either a central RSVP stream or a moving-dot stimulus (adaptor) in the periphery (31.5° eccentricity). We measured the motion aftereffect (MAE) via a speed nulling procedure. The difference in MAE strength between attending to the adaptor versus the RSVP stream was used to quantify the effect of space-based attention. We found attending to the adaptor yielded a larger MAE than attending to the RSVP stream, for both the normal and rotated sitting positions, equally for both hemifields. In Experiment 2, we manipulated feature-based attention by instructing participants to attend one of two superimposed moving dot fields at the center of the screen. The MAE was then measured in two peripheral locations, similar to Experiment 1. The MEA induced by attending to upward vs. downward motion was used to quantify the effect feature-based attention. We found attention-induced MAE spread equally to both hemifields regardless of sitting position. In conclusion, the ability to make an eye movement to a location is not necessary for either endogenous space- or feature-based attention to operate at that location.
Meeting abstract presented at VSS 2018