Searching over time: A study of attention using preview search

Attention is the mechanism that enables us to process the sensory information most relevant to our current goals. As our most dominant sense, the way in which we attend to the visual environment is a highly important and highly researched topic (Sperling, 1960; Eriksen & Eriksen, 1974; Posner, 1980). One such method of examining visual attention is using a visual search task, where participants must locate a specified target amid distractors and their reaction times and accuracy are recorded (Treisman & Gelade, 1980; Duncan & Humphreys, 1989; Wolfe, Cave & Franzel, 1989) to gain an understanding of how attention can be guided through an array of items. Using a particular variant of the visual search task known as preview search (Watson & Humphreys, 1997), the purpose of this thesis is to extend our understanding of visual attention by examining how and if we can ignore stimuli known to be irrelevant, and if prior knowledge and expectation can guide attention effectively. Chapter 1 examines the effect of a concurrent task on performance, and suggests the timing of a concurrent task as well as the modality impact the efficiency of search. Chapters 2 and 3 examine the role of prior knowledge and expectation on search and show that the usefulness of expectation depends on the type of prior knowledge (e.g. a property or the location of the stimuli). Chapter 4 examines the role of emotion and whether a negative face can be ignored, with the results suggesting preferential selection of faces viewed face-on, rather than in profile. Results of the experiments are discussed in relation to theories of preview search.