Oculomotor Evidence for Top-Down Control following the Initial Saccade

Alisha Siebold,Mieke Donk,Wieske Van Zoest,Adrian G Dyer

doi:10.1371/journal.pone.0023552

Abstract

The goal of the current study was to investigate how salience-driven and goal-driven processes unfold during visual search over multiple eye movements. Eye movements were recorded while observers searched for a target, which was located on (Experiment 1) or defined as (Experiment 2) a specific orientation singleton. This singleton could either be the most, medium, or least salient element in the display. Results were analyzed as a function of response time separately for initial and second eye movements. Irrespective of the search task, initial saccades elicited shortly after the onset of the search display were primarily salience-driven whereas initial saccades elicited after approximately 250 ms were completely unaffected by salience. Initial saccades were increasingly guided in line with task requirements with increasing response times. Second saccades were completely unaffected by salience and were consistently goal-driven, irrespective of response time. These results suggest that stimulus-salience affects the visual system only briefly after a visual image enters the brain and has no effect thereafter.

Highlights

Imagine you are looking for your friend in a large shopping mall crowded with people
Performance accuracy in selecting the target was investigated as a function of saccadic latency and the results indicated that goaldriven processes increased as a function of response latency. These results indicate that the timing of a response within an initial eye movement is crucial in determining the contribution of both salience-driven and goal-driven processes to overt visual selection
A similar procedure was followed for the classification of second saccades, with the exception that the gaze proportions of only two singletons were examined per bin

Summary

Introduction

Imagine you are looking for your friend in a large shopping mall crowded with people. Empirical evidence does show that salient objects or features in the visual field receive selective priority by attracting attention and the eyes [1,2,3,4,5,6,7] This evidence is primarily derived from reaction time (RT) studies [8,9,10,11,12,13] and studies in which the results are based on the analysis of participants’ initial eye movements only [14,15,16,17,18,19,20]. Studies examining overt visual selection behavior under freeviewing conditions, i.e. those in which multiple eye movements are made, do not provide unequivocal evidence for the idea that visual selection is salience-driven [21,22,23,24,25,26,27,28,29,30,31,32,33,34]

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