Negligible effect of spatial precuing on identification of single digits.

The present study examined the effects of spatial preening on identification of a single object appearing in an otherwise empty visual field. A digit target was preceded by a valid, neutral, or invalid location cue, presented either peripherally or centrally. The target was followed by either a single mask or multiple masks covering the target and nontarget (empty) locations. Precuing significantly affected identification accuracy when multiple masks were used but had little effect when the target was followed by a single mask. The results strongly favor a model in which spatial precuing allows the contents of noncued locations to be excluded from decision (and possibly perception). Exclusion may or may hot facilitate performance, depending on what is there to be excluded. The role of spatial visual attention in modulating perception has intrigued psychologists for a long time. Helmholtz (1866/1924) noted that in a completely dark room, a person can concentrate his attention on any part of the room, so that when a spark of light illuminates the whole room, he will get an impression about the objects in that particular region only. Because the spark is too brief for an eye movement, Helmholtz reasoned that covert orienting of attention must be independent of the position and accommodation of the eyes. Modern experimental psychologists have adopted similar paradigms, albeit with better experimental controls, to study voluntary and involuntary deployment of spatial attention. In a typical experiment of this kind, a target appears in one of several locations. The manipulation of spatial attention is supposed to be accomplished by presenting a location cue shortly before the target display. This precue is valid when it indicates the location of the target. It is invalid when it cues a location where the target does not appear. It is neutral if it carries no information whatsoever about the location of the target. Researchers have examined effects of both peripheral cues (appearing near the location of the target) and