UBC Theses and Dissertations
Greater distractor interference during vertical saccades : the time course of horizontal, vertical, and oblique saccadic curvature Laidlaw, Kaitlin Elizabeth Wiggins
In three studies, we characterize the effect of a nearby distractor on vertical, horizontal and oblique saccadic curvature under normal saccade preparation times. In Experiments 1 and 2, participants made saccades to targets in the presence or absence of a nearby distractor. Consistent with previous findings, longer-latency vertical saccades showed greater curvature away from a distractor than did oblique or horizontal saccades. At short latencies, vertical saccades showed greater curvature towards the distractor. We propose that vertical saccades may be prone to greater distractor interference due to the superior colliculus, a midbrain region implicated in attentional and saccadic shifts, under-representing vertical target objects, which results in a relative over-representation of non-vertical distractor objects. In Experiment 3, we tested this hypothesis by having participants make saccades to vertical or horizontal targets in the presence or absence of bright or dim distractors. We reasoned that weaker representations for vertical targets would allow for greater interference from nearby distractors, which would be especially pronounced when distractors are highly salient. Consistent with this prediction, we found that only the trajectory of vertical saccades was modulated by distractor luminance.
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