John McDonald¹, Rebecca Carson¹, Daniel Tay¹; ¹Simon Fraser University

A recent attempt to resolve a longstanding debate failed to reach consensus about whether and when salient visual distractors capture attention. Part of the problem may stem from the limited way in which salience is conceptualized in the majority of attention-capture studies. In particular, although people can rapidly detect salient changes in visual stimulation across time, salience is usually defined solely in term of stimulus contrast within individual displays. Here, we integrated the visual search paradigm with the oddball paradigm to investigate the relative contributions of instantaneous spatial salience and temporal salience in the determination of visual selection. In all experiments, infrequent target and nontarget displays were randomly interspersed with frequent standard displays that contained three blue, vertical bars on each side of fixation (herein called standard bars). Participants were instructed to press a button when they noticed a display containing a specific number of yellow items, which varied across experiments. In Experiment 1, all standard bars on one side of fixation were replaced with yellow vertical bars (colour change) or blue horizontal bars (orientation change) to create target and nontarget displays, respectively. Neither of these displays contained any instantaneously salient item, but the target and nontarget bars (herein called change items) still popped out because they differed substantially from standard displays (temporal salience). To determine how the change items were processed, we looked for event-related potential activities associated with deviance detection (visual mismatch negativity), attentional selection (N2pc) and suppression (PD). In Experiment 1, target and nontarget change items triggered the N2pc, which indicates that temporally salient items can capture spatial attention when they are not (instantaneously) salient within individual displays. These results will be discussed in relation to current theoretical perspectives, including salience-driven selection theory, signal suppression theory, and dimension weighting theory.

Acknowledgements: Funded by NSERC