Visuospatial attention: the role of target contrast and task difficulty when assessing the effects of cues

Cueing paradigms have become popular in assessing the processes of attentio n. In two experiments we manipulated (i) the contrast of the target, and (i i) the similarity between the targets discriminated. We used a cue that wou ld isolate the exogenous component of attention. Both a reduction in target contrast and an increase in target similarity raised overall reaction time s by a similar amount; however, the target contrast manipulation produced a much greater cueing effect compared with the target similarity manipulatio n. The results suggest that manipulation of target contrast changes the att ention cueing effect at a stage of attracting attention to a location of th e target (the 'move' stage), rather than at a later processing stage.