Temporal changes in the distribution of attention in the visual field in response to precues.

Abstract

This experiment measured the changes in the distribution of attentional processing in the visual field in response to precues. The hypothesis of an analogue movement of the attentional “spotlight” across the visual field was also tested. Choice reaction time to stimuli was determined in a response competition paradigm. Subjects viewed a central fixation point and the stimuli (the letters A and U) were presented at retinal eccentricities of 1°, 2°, and 3° along the horizontal meridian to the left and right of fixation. Two letters were simultaneously presented in all experimental conditions. For compatible noise, the second letter was identical to the target, and for incompatible noise, the second letter was the other letter of the target set. The target letter in a trial was designated by an underline that either occurred simultaneously with the onset of the two-letter display or preceded the display by 25, 50, 75, 100, or 175 msec. The target letter occurred equally often in each of the six display positions and the noise letter equally often in each of the remaining positions. The response competition effect of an incompatible noise letter was found to be a joint function of target and noise-letter location, an effect that changed over time from onset of the underline precue to the onset of the display. With simultaneous onset, interference was largely independent of target and noise location, but with increasing asynchrony of onset, noise interference became increasingly confined to locations adjacent to the target. No evidence was found for an analogue movement of an attentional “spotlight” across the visual field.