Abstract
Does an attentional shift take more time as the distance gets larger? Many studies have been conducted trying to answer this question; the answer is sometimes yes (e.g. Tsal, 1983) and sometimes no (Remington & Pierce, 1984). The current investigation also addressed this question, but did so by separately measuring the speeds of exogenous and endogenous shifts of attention. On every trial, attention was first pulled to the periphery by a luminance change, and then was voluntarily moved to another stimulus that always appeared at fixation. Therefore, the shift distances and times of both types of attentional shift were measured successively; that is, each trial contained an exogenous phase and an endogenous phase. It was found that the traveling time of the exogenous shift was statistically dependent on distance, with shifts requiring approximately 2 ms per degree of visual angle when the retinal eccentricity of the display was greater than 1°. This effect of distance was not found in the data from the endogenous phase. These results are consistent with both Tsal (1983) and Remington and Pierce (1984). Thus, our data provide another piece of evidence that an attentional shift triggered by an exogenous event has a different spatio-temporal property than triggered by endogenous intention.