Covert orienting: a compound-cue account of the proportion cued effect.

An increase in the proportion of spatially cued trials in the context of the covert orienting paradigm increases the magnitude of the cuing effect. This proportion cued effect is widely interpreted to reflect a form of control. Specifically, it is argued that participants strategically allocate attention as a function of the utility of the spatial cue. Here, an alternative explanation of the proportion cued effect is proposed that does not require control. According to this account, the cue-target event forms a compound cue and the proportion cued manipulation produces a relative disparity in the frequency with which particular compound cues occur. Specifically, when the proportion of spatially cued trials is increased, the frequency of spatially cued cue-target events increases and the frequency of spatially miscued cue-target events decreases, thus increasing the magnitude of the cuing effect. The results of two experiments support this account.