Differential involvement of the oculomotor system in covert visual search and covert endogenous cueing

摘要

The relationship of spatial attention to eye movements has been controversial. Some theories propose a close relationship, while others view these systems as completely independent. In a recent study using a cueing task we proposed that this controversy can be resolved by distinguishing between the maintenance and shifting components of attention (Belopolsky & Theeuwes, 2009; Psy Science). Specifically, we proposed that shifting covert attention is always associated with preparation of saccade, while maintaining attention at a location can be dissociated from saccade preparation. The current study tests the boundary conditions of this proposal. Experiment 1 used a visual search task in which repeated serial shifts of attention were required in order to find the target. The identity of the target indicated whether an eye movement towards the target or a non-target location had to be made. The results indicated that saccades were initiated faster towards the location where covert attention was shifted. Experiment 2 used endogenous cueing manipulating the SOA between the cue and the appearance of the target. The results showed suppression of saccade in the direction of the covert attention shift even at the shortest SOA. The findings suggest that shifts of attention during covert visual search are associated with activation of an oculomotor program, while shifts of attention during covert endogenous cueing are associated with suppression of an oculomotor program. This suggests that distinction between endogenous and exogenous covert shifts of attention is important when relationship between attention and eye movements is investigated. We propose that only during pure endogenous covert shifts of attention can the oculomotor system be suppressed. In addition and consistent with previous findings (Wolfe, Alvarez & Horowitz, 2000), our results implicate that shifts of attention during covert visual search are not purely endogenous.