THE ROLE OF ATTENTION IN THE PROGRAMMING OF SACCADES

Accurate saccadic programming in natural visual scenes requires a sign al designating which of the many potential targets is to be the goal o f the saccade. Is this signal controlled by the allocation of perceptu al attention, or do saccades have their own independent selective filt er? We found evidence for the involvement of perceptual attention, nam ely: (1) summoning perceptual attention to a target also facilitated s accades; (2) perceptual identification was better at the saccadic goal than elsewhere; and (3) attempts to dissociate the locus of attention from the saccadic goal were unsuccessful, i.e. it was not possible to prepare to look quickly and accurately at one target while at the sam e time making highly accurate perceptual judgements about targets else where. We also studied the trade-off between saccadic and perceptual p erformance by means of a novel application of the ''attentional operat ing characteristic'' (AOC) to oculomotor performance. This analysis re vealed that some attention could be diverted from the saccadic goal wi th virtually no cost to either saccadic latency or accuracy, showing t hat there is a ceiling on the attentional demands of saccades. The lin ks we discovered between saccades and attention can be explained by a model in which perceptual attention determines the endpoint of the sac cade, while a separate trigger signal initiates the saccade in respons e to transient changes in the attentional locus. The model will be dis cussed in the context of current neurophysiological work on saccadic c ontrol.