Irrelevant speech and irrelevant tones: The relative importance of speech to the irrelevant speech effect

Irrelevant auditory stimuli disrupt immediate serial recall. In the equipotentiality hypothesis, D. M. Jones and W. J. Macken (1993) made the controversial prediction that speech and tones have an equivalent disruptive effect. In the present study, 5 experiments tested their hypothesis. Experiments 1-4 showed that meaningful speech disrupts recall more than do tones. Experiments 3 and 4 provided some evidence that meaningful speech disrupts recall more than does meaningless speech, and Experiment 4 showed that even meaningless speech disrupts recall more than do tones. Using slightly different experimental procedures, Experiment 5 showed that letters disrupt recall more than do tones. Implications of these results for a number of theories of primary memory and the irrelevant speech effect are discussed.