Attention and oculomotor capture

The investigations contained in this thesis explore distraction during visual search, with particular attention to what eye movements can reveal about the processes involved in visual search. All the experiments make use of the oculomotor capture effect, whereby an eye movement is misdirected toward a sudden onset distractor before being redirected to a target object. Fundamental differences between eye movements and attention in general, and between eye movements and manual responses in particular, support the current view that oculomotor capture is distinct from the more general effect known as attentional capture. Like oculomotor capture, attentional capture involves interference with visual search for a target by distractors. Unlike oculomotor capture, this interference is expressed as a delayed correct manual response, rather than a misdirected eye movement. The first study shows that resolution of oculomotor conflict between target and distractor responses takes place at or above the level of the superior colliculus, a midbrain structure involved in eye movement control. The second study explores the timecourse of eye movement and manual localization responses to targets in the presence of sudden onsets, and suggests that for both response types, capture reflects the quality of information about the visual display at a given point in time. The final study expands the oculomotor capture effect to search among emotional faces and finds that the eyes are captured by emotional faces more than neutral distractors only if emotion is task-relevant. Together, the research suggests that oculomotor capture is a specific instance of the more general attentional capture effect. It is proposed that differences and similarities between the two types of capture can be explained by the critical idea that the quality of information in a visual display changes over time, and that different response systems tend to access the same information at different moments in time.Arts, Faculty ofPsychology, Department ofGraduat