Expectancy and dual-task interference.
This research deals with the relationship between expectancy and attention. In two experiments, expectancy concerning the modality of a probe stimulus was manipulated. In Experiment 1, the frequencies of probes in auditory and visual modalities were varied. In Experiment 2, a cue prior to each trial indicated the relative probabilities of the two types of probes. In both experiments, expectancy effects were observed in a single-task condition during which the subject's only task was to respond to the probes and in a dual-task condition in which probes were inserted in the study phase of a pattern recognition task. If maintaining an expectancy requires attention, then diverting attention from the probe task to the pattern recognition task should have attentuated the effects of expectancy. In fact, the pattern recognition task did not alter frequency effects but did significantly reduce cueing effects. We conclude that expectancy as determined by frequency results from automatic activation, whereas expectancy as determined by cueing involves attention.