Effects of spatial and symbolic precues on localization performance

One of the fundamental properties of spatial vision is the ability to local ize objects in space. According to a recent proposal, accurate localization performance involves the operation of two systems: the attention system an d the eye movement system. Upon stimulus presentation, attention is shifted to the target area: this provides coarse location information. Subsequentl y, a saccadic eye movement is executed: this provides fine location informa tion. In this study we tested predictions derived from this model concernin g the effects of precue information on localization performance. In a serie s of five experiments we manipulated duration of precue (71, 400, and 1,000 ms) and type of precue (spatial versus symbolic). Results showed that very short duration (i.e., 71 ms) spatial precues improved localization perform ance whereas very short duration symbolic precues did not. In contrast, the 1,000 ms duration precue condition showed similar amounts of precuing bene fit for the spatial and symbolic precues. This pattern of differential prec uing effects corroborated the two-process model of localization performance .