Chapter 4 - Saccadic Selectivity During Visual Search: The Influence of Central Processing Difficulty

Abstract

This chapter examines the robustness of guidance of eye movements during visual search. Visual search is one of the dominant paradigms used for investigating visual attention. In a typical visual search task, participants have to decide whether a search display contains a designated target among distractors (nontarget elements). Consistent with major visual search theories, experiments discussed in the chapter demonstrate that participants direct their saccades selectively during the search process, revealing a strong correspondence between target-distractor similarity and saccadic frequency toward the respective distractors. While the duration of current fixations increased with increasing target-distractor similarity, there was no evidence that saccadic selectivity was influenced by the target-distractor similarity of the previously fixated display item or the duration of the previous fixation. These findings are inconsistent with the predictions by the waiting-room model. The chapter manipulates the difficulty of the central discrimination by introducing a concurrent visual task and presenting a gaze-contingent moving foveal mask. Although manipulations substantially degraded the overall visual search performance, the magnitude of peripheral selection was not affected. This is not consistent with the notion that the central discrimination and the peripheral analysis share the same pool of attentional resources as suggested by the foveal load model. Thus, these experiments provide convergent evidence that peripheral selection is a robust process, largely independent of the central processing difficulty.