The dark side of visual attention : situational factors and individual differences in inattentional blindness

Abstract

Inattentional blindness (IB) occurs when an individual does not notice a salient but unexpected object or event because their attention is engaged by another task. Previous research into IB predominantly focused on how manipulating stimulus characteristics or task demands affects rates of lB. This thesis extends existing research by examining IB in relation to other phenomena including eye movements and cross-modal attention, and examining the effect of individual differences in general attentional processes. There are six empirical chapters addressing various aspects of IB research. The first empirical chapter investigates whether IB knowledge predicts the incidence of lB. Most prior research excluded participants with any knowledge of IB, claiming they would "expect the unexpected". This chapter demonstrates that it is possible to use non-na{u00EF}ve participants in IB experiments under certain circumstances, which is relevant since most potential participants possess some knowledge of lB. The second empirical chapter used a video eye tracker to investigate the role of eye movements in lB. The results reveal that eye movements do not predict IB; in both experiments several participants failed to notice the unexpected stimulus despite directly fixating on its location, while other participants detected the stimulus without fixating on or near it. The third and fourth empirical chapters investigate the effects of crossmodal attention on lB. These chapters address the effects of listening to concurrent audio stimuli and talking on a cellular telephone during IB tasks. Conversing on a hands-free phone significantly impairs observers' ability to detect a highly salient stimulus. Simply talking without a conversation partner (e.g., leaving a voicemail message) also significantly increases lB. In contrast, simply listening to audio stimuli (e.g., voicemail, short stories, music) typically has no effect on IB but can actually decrease IB under some conditions, particularly when the primary visual task has low perceptual load. The fifth and sixth empirical chapters examine individual differences in lB. The fifth empirical chapter examines the relationship between IB and attentional blink (AB), another failure of visual awareness. Observers who experienced IB also experienced AB, suggesting that some people are generally more susceptible to failures of conscious awareness regardless of whether they result from the distribution of attention across space (IB) or time (AB). The sixth empirical chapter explores whether specific cognitive traits or processing styles predispose individuals to experiencing lB. Self-report measures of distractibility and immersion do not predict IB, however, individual tendencies towards rumination and task-unrelated thoughts do predict lB. Together these studies help situate IB within the broader framework of attention research and theory. Previous research tended to look at IB in isolation, with few links to other cognitive phenomena. Past studies also involved a strong stimulus focus, which gave us insight into which unexpected events were most likely to be noticed. The current thesis extends past research and forms part of a new programme of IB research, which is focused more on individual observers and providing insight into who is most likely to notice unexpected objects and why, with consideration given to both personal and characteristics.