Manipulations of the relationship between response alternatives and exogenous saccade latencies.

The relationship between the latencies of saccadic eye movements and the number of response alternatives is complex. Previously, we have found a decrease in exogenous saccade latencies with an increase in the number of response alternatives (i.e., an anti-Hick's effect). In the present study, we examined the effect of bottom up and top down influences on the effect. In Experiment 1, we found that the anti-Hick's effect is dependent upon the number, as opposed to the configuration, of response alternatives, suggesting that the effect is not a purely bottom up phenomenon. In Experiment 2, we examined whether top down processes, such as expectancy, influence the magnitude and/or direction of the relationship between response alternatives and reaction time. We found that interleaving, as opposed to blocking, the number of alternatives negated the anti-Hick's effect. Taken together, these results suggest that the anti-Hick's effect arises not only from stimulus-based perceptual signals but also from higher-order control signals.