Natural boundaries for the spatial spread of directed visual attention.

The spatial characteristics of directed attention were studied using spatial precues in a suprathreshold luminance detection task. Visual response times to probe flashes presented at various distances from the presumed focus of attention provided the dependent measure. The variation in response times with distance from the attentional focus was used to create spatial maps of the expectancy effect. The results indicate that, in an uncluttered visual field, the effects of precuing are widely distributed, and that the principal transitions in performance tend to occur either at the horizontal meridian, the vertical meridian, or both meridians, depending on the locus of the observers' expectancy.