The irrelevant sound effect: Does speech play a special role?

Memory for order is markedly impaired by the presence of irrelevant sound, even though participants are instructed to ignore the sound. Although a great deal of research has disclosed some features of the task and of the sound that augment or reduce the degree of interference, one important issue of the irrelevant sound effect not yet resolved is whether speech has a special 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 disruptive 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.