Abstract
Animals reflexively orient toward unexpected events. If these events are repeated without consequence, there is a decrement in orienting called habituation. It has been proposed that one aspect of human spatial attention, inhibition of return (IOR), is best understood as an instance of habituation (Dukewich, 2009; Huber, 2008). Consistent with this account, increasing the number of non-predictive cues, and increasing their rate, both lead to greater IOR (Dukewich & Boehnke, 2008). This study examines an untested premise of the habituation account of IOR, namely, that attentional orienting is necessary for habituation to occur in the first place. If habituation only occurs to attended events, it should be reduced when cues hold less information with respect to the primary task of target identification. We manipulated cue information by varying temporal predictability. In a fixed-cue condition, either 1, 3, or 5 non-predictive spatial cues were presented at one of three rates of presentation, leading to a pattern of results consistent with the known characteristics of habituation. A jittered-cue condition was identical, except that a time jitter of ± 100 ms was added to the rate of presentation, making the event sequence within a trial less predictable. Although participants in both conditions showed increased IOR as the time between the first cue and the target was increased, cue number had an influence in the fixed, but not in the jittered, condition. In addition, this difference was largest in the fastest rate of presentation, where the added jitter had the greatest effect on event predictability. These results establish the importance of initial orienting for habituation to occur in a spatial attention task. Temporal uncertainty among the cues and targets reduces orienting to individual cues, thuspreventing the buildup in habituation otherwise associated with successive, predictable, cues.
Natural Sciences and Engineering Council.