Organizational factors in the effect of irrelevant speech: the role of spatial location and timing.

Typically, hearing a repeated syllable produces minimal disruption of serial recall of visual lists, but a sequence of different syllables impairs performance markedly. Two conditions for presenting an identical sequence of three syllables are compared: one, in which, by means of stereophony, each syllable is assigned to the left, center, or right auditory locus (three streams not changing in state), and another, in which the same syllable sequence occurs in one location only (one stream with changing state). Disruption was significantly less in the stereophonic than in the monophonic condition. There was a joint effect of changing state and location, not an effect of the number of locations alone. In Experiment 2, temporal predictability was used to manipulate changing state. The disruptive effect of regular presentation of a repeated syllable was markedly increased when it was presented irregularly. The results are discussed in the context of organizational factors in short-term memory.