Extending the irrelevant speech effect beyond serial recall.

The irrelevant speech effect is the impairment of immediate memory by the presentation of to-be-ignored speech stimuli. The irrelevant speech effect has been limited to serial recall, but this series of 8 experiments demonstrates that it is considerably more general. Experiments 1-3 show that (a) irrelevant speech inhibits free recall more than does white noise, (b) irrelevant speech impairs free recall even when the speech occurs after the to-be-recalled items, and (c) free recall is inhibited even when the speech is meaningless. Experiment 4 failed to find an effect in free recall with 16-item lists. Experiments 5A-5C extend the effect to recognition of 8-, 12-, and 16-item lists, with both phonologically related and phonologically unrelated lure items. Experiment 6 extends the effect to a cued recall task that discourages the use of serial rehearsal of the to-be-remembered items.