Asymmetrical processing within the visual field during visual search

McCadney-Vines, Rotchie, and Harold H. Greene

(To be presented at the 2011 Mid-America Undergraduate Psychology Research Conference)

Experiments with briefly-presented stimuli (30ms-150ms) indicate asymmetrical sensitivity within the visual field.  However, brief presentations do not reflect search conditions. Here, saccade distances were used to describe visual field sensitivity during visual search of a random-dot display.  Brief-presentation results predict (i) longer saccades towards the lower than the upper visual field (i.e. VMA), and (ii) a wider saccade span along the  horizontal than vertical visual field (i.e. HVA).  Saccade distances were analyzed in a 2 Fixation Duration (Brief: duration <  150 ms  vs Long: duration> 150 ms) X  8 Saccade Compass Direction (N NE …) model.  The interaction was significant, and was analyzed on VMA and HVA expectations.  For brief fixation durations, there was no VMA. However,  an HVA was present.  For long durations, there was a VMA, and an HVA for the upper visual field. Sensitivity to stimuli during visual search may not be independent of fixation duration.