Alerting effects occur in simple-But not in compound-Visual search tasks

Alerting (e.g., a brief brightening of the screen just before a target display) is known to facilitate visual search in simple tasks that involve the single step of detecting a pop-out item within a stimulus array. What is not known is whether alerting facilitates performance also in compound search tasks which involve two steps: First, locate the pop-out item, then identify a detail of that item. In a series of five experiments, we show that alerting facilitates performance of each component of a compound task when tested separately, (Experiments 2a and 2b) but not when the components are combined in a compound task (Experiment 1). Yet, alerting does facilitate performance in a compound task when the pop-out item is displayed in the same location on successive trials (Experiment 3). We hypothesized that such spatial repetition allows attention to linger at that location, thus allowing the first component (locate the pop-out item) to be bypassed. In practice, this turns the compound task into a simple task. That hypothesis was confirmed in Experiment 4 using a reorienting cue to shift the focus of attention to another location. An overall account of the absence of alerting effects in compound search tasks is proposed in terms of the temporal relationship between a period of enhancement rendered as an ex-Gaussian function and the hypothesized sequence of processing stages in visual search. (PsycInfo Database Record (c) 2022 APA, all rights reserved).