Abstract
Eye movements are critical for identifying and acting in response to visual threat stimuli. Saccades are produced by a highly streamlined system that is immune to response uncertainty, with simple stimulus-response associations, while manual responses are strongly affected by response uncertainty (Kveraga, Boucher and Hughes, 2002; Kveraga & Hughes, 2005). The aim of this study was to examine how saccadic and manual responses would be affected by more complex stimulus-response uncertainty, in which subjects had to select between negative (clear or ambiguous threat) and neutral scene images. We presented images of scenes depicting clear threat or ambiguous negative situations along with neutral scene images. The two images were presented bilaterally on the left and right side of the screen while we recorded subjects’ (N=57) saccades and manual responses. The task was to detect the scene image which depicted harm and respond to that side with the corresponding hand as quickly and accurately as possible. The paired scene stimuli were matched in general context, but differed in affective tone. Subjects were faster to make a saccade to clear threat images than to ambiguous threat images, but only when the clear threat scenes appeared in the left visual field (LVF): responses to clear threat were not significantly faster than responses to ambiguous negative stimuli overall. Conversely, the manual responses were faster to all negative stimuli presented in LVF, consistent with previous reports, and were faster bilaterally for clear threat vs. ambiguous negative scenes. Lastly, saccadic responses were much faster (by ~600 ms) than manual responses, but the saccadic response times (RT) did not predict the RT of the matching manual responses. We conclude that saccadic and manual responses to clear and ambiguous threat scenes follow different response patterns, with no overall LVF or clear threat RT advantage for saccades.
Meeting abstract presented at VSS 2015