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Abstract:
Reflexive saccades are fast eye movements that follow the sudden appearance of a salient visual stimulus in the visual field. This reflexive orienting mechanism could have evolved to enable quick evaluations of sudden changes in the environment and, in doing so, support potentially vital actions (e.g., flight). In light of this, it is surprising that reflexive saccades have mostly been studied with tasks that do not require the saccade to support a perceptual
judgment. In the current study we measured properties of reflexive saccades in two conditions: In one condition, the saccade enabled the performance of an object discrimination task (discrimination), in the other, it did not (fixation). In the discrimination task, participants made reflexive saccades following the sudden onsets of Landolt squares (0.1 deg. visual angle) and decided if these squares had an opening at the top or bottom. In the fixation task, the same
squares were presented but without an opening. Here participants were instructed to fixate the squares as quickly as possible. The results show that saccades supporting a discrimination task are faster and are initiated earlier than saccades that do not enable the completion of such a task. This demonstrates that reflexive saccades could be influenced by the demands of the task. Possible task-specific factors could include the difficulty of the task, time pressure, or the reward associated with completion of the task.
