Reaction times in a bisensory task: implications for attention and speech perception.

Reading reaction time (RT) to visual stimuli was shown to vary according to the nature of simultaneous auditory stimuli. In Experiment 1, simultaneous different digits produced slower RTs than a burst of speech noise, while identicaly digits produced faster RTs. In Experiments 2 and 3 the stimuli were phoneme pairs which differed on either zero, one, or two articulatory features. Identical phonemes resulted in the fastest RTs. The RTs to non-identical phoneme pairs were not directly related to the number of differing features but were dependent upon the specific feature involved. A two-stage model was proposed to explain the results in which parallel processing of simultaneous input occurs prior to a decision-making stage.