Change of intensity fails to produce an irrelevant sound effect: Implications for the representation of unattended sound

Sequences of changing sounds that are irrelevant to the task at hand disrupt serial recall appreciably even though participants are instructed to ignore the sounds. Three experiments, which compared the effect of changing token identity with that of changing intensity in the 55- to 85-dB(A) range, were conducted. Although serial recall was impaired by changes in token identity, no disruptive effects of a change in intensity were found. This was replicated using speech and nonspeech. Overall, the absence of a changing intensity effect was based on an analysis of the performance of 115 participants in a design whose power was .98. This outcome suggests that the representation of intensity in preattentive processing of auditory stimuli is somewhat different from that of other acoustic features.