Memory for order is markedly impaired by the presence of irrelevant sound,
even though participants are instructed to ignore the sound. Although a gre
at deal of research has disclosed some features of the task and of the soun
d that augment or reduce the degree of interference, one important issue of
the irrelevant sound effect not yet resolved is whether speech has a speci
al status. This study revealed, within a design of adequate power, that the
same physical stimulus (sine wave speech), whether perceived as speech or
as nonspeech sound, produces similar degrees of disruption and is less disr
uptive of serial recall than natural speech. This outcome suggests that the
acoustic constituents of sound rather than its source are most influential
in determining the impact of irrelevant material.