Non-Informative Effects of Stimuli Functioning as Cues

The category of a first stimulus (S₁) serving as a cue may allow a subject to predict the category of a second stimulus (S₂). However, a cue may have effects on RT to S₂ 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 S₁ is in the same category as S₂ (as is frequently the case for valid cues in cueing experiments) but provides no information about S₂, RT is slower than when S₁ is in a different category from S₂. It is suggested that this category relation effect arises because inhibition of a response to S₁ is still present when S₂ arrives and that, in some cueing experiments, it may subtract from the RT benefits derived from the cue as a predictor of S₂. Also, RT to a visual but not to an auditory S₂ was faster after an auditory S₁ than after a visual S₁. 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.