Action modulates object-based selection

Cueing attention to one part of an object can facilitate discrimination in another part (Experiment 1 [Duncan, j. (1984). Selective attention and the organization of visual information. Journal of Experimental Psychology: General, 113, 501-517]; [Egly, R., Driver, J., and Rafal, R. D. (1994). Shifting visual attention between objects and locations: evidence from normal and parietal lesion divisions. Journal of Experimental Psychology: Human Perception and Performance, 123, 161-177]). We show that this object-based mediation of attention is disrupted when a pointing movement is prepared to the cued part; when a pointing response is prepared to a part of an object, discrimination does not differ between (i) stimuli at locations in the same object but distant to the part where the pointing movement is programmed and (ii) stimuli at locations equidistant from the movement but outside the object (Experiment 2). This remains true even when the pointing movement cannot be performed without first coding the whole object (Experiment 3). Our results indicate that pointing either (i) emphasizes spatial selection at the expense of object-based selection, or (ii) changes the nature of the representations(s) mediating perceptual selection. In addition, the results indicate that there can be a distinct effect on attention of movement to a specific location, separate from the top-down cueing of attention to another position (Experiment 3). Our data highlight the itneractivity between perception and action