The effect of irrelevant information on the stages of processing.

The Sternberg (1969) additive factor method was used to determine whether the stimulus encoding stage was affected by an irrelevant auditory stimulus presented during a visual choice reaction time task. Subjects responded to an X or an O by pressing a left-or right-hand key. Onset of this visual stimulus was accompanied by a tone to the left, right, or both ears. Reactions were slower when the locus of the tone did not correspond with the side of the response than when it did correspond. Manipulation of the quality of the visual stimulus, assumed to affect the stimulus encoding stage, did not alter the effect of the irrelevant auditory cue. In a parallel experiment, the same stimuli were used, but the responses employed were "neutral" with respect to the source of the tone. This alteration of response selection operations eliminated the effect of the auditory cue. Findings, then, suggested that irrelevant information did not affect the stimulus encoding stage but, instead, affected the response selection stage of processing.