Non-Informative Effects of Stimuli Functioning as Cues

The category of a first stimulus (S 1 ) serving as a cue may allow a subject to predict the category of a second stimulus (S 2 ). However, a cue may have effects on RT to S 2 that are independent of those derived from its intended role as a predictor. These non-informative effects of a cue may add to or subtract from the benefits associated with its predictive function. Two experiments demonstrate that when S 1 is in the same category as S 2 (as is frequently the case for valid cues in cueing experiments) but provides no information about S 2 , RT is slower than when S 1 is in a different category from S 2 . It is suggested that this category relation effect arises because inhibition of a response to S 1 is still present when S 2 arrives and that, in some cueing experiments, it may subtract from the RT benefits derived from the cue as a predictor of S 2 . Also, RT to a visual but not to an auditory S 2 was faster after an auditory S 1 than after a visual S 1 . It is argued that this modality combination effect is consistent with the view that auditory signals are more alerting than visual ones and that this is another factor to be taken into account in the design of cueing and other experiments.