Irrelevant speech disrupts immediate recall of a short sequence of items. Salame and Baddeley (1982) found a very small and nonsignificant increase in the irrelevant speech effect when the speech comprised items semantically identical to the to-be-remembered items, leading subsequent researchers to conclude that semantic similarity plays no role in the irrelevant speech effect. Experiment 1 showed that strong free associates of the to-be-remembered items disrupted serial recall to a greater extent than words that were dissimilar to the to-be-remembered items. Experiment 2 showed that this same pattern of disruption in a free recall task. Theoretical implications of these findings are discussed.A robust finding in immediate memory is that, despite explicit instructions to the contrary, background speech significantly disrupts short-term memory (e.g., Colle & Welsh, 1976;Jones, Madden, & Miles, 1992;LeCompte, 1994LeCompte, , 1995LeCompte, , 1996Salame & Baddeley, 1982). A typical irrelevant speech effect experiment could be described as follows: Participants are presented with a list of seven to nine items on a computer screen at a rate of one or two items per second. During the visual presentation, participants hear either nothing or spoken words. After the presentation of the visual items, participants are asked to recall these items in serial order-that is, in the order they were presented. The typical finding is that recall of the visual items is significantly worse with the speech background than with the quiet background. Note, however, that although the irrelevant speech effect is usually demonstrated with visual stimuli, it is also found with auditory stimuli (see, e.g., LeCompte, 1996), and although irrelevant speech is the usual disruptive agent, tones have also been shown to disrupt memory (see, e.g., Jones & Macken, 1993), although to a lesser extent than speech (LeCompte, Neely, & Wilson, 1997).Perhaps the most basic question about the irrelevant speech effect concerns the mechanism by which irrelevant speech interferes with short-term memory. Two theories have been proposed to explain this interference. Each theory offers a different mechanism for the interference.The first theory, the phonological store hypothesis of Baddeley (1982, 1989), proposes a store that holds information in a strictly phonological form. According to the hypothesis, speech has obligatory access to the phonological store. Visual information also enters 37this store, but it must be coded phonologically through an active process ofsubvocal rehearsal. While these two types of information are together in the phonological store, the auditory information interferes with the visual information, thereby degrading recall of the visual information. The degree of interference is a function of the phonological similarity between the background speech and the visual information.The second theory, the changing state theory of Jones and his colleagues (e.g., Jones, 1993Jones, , 1995Jones, Beaman, & Macken, 1996;Jones & Macken, 1993; Jones ...

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.

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Experimental efforts to meliorate the modality effect have included attempts to make the visual stimulus more distinctive. McDowdand Madigan (1991) failed to find an enhanced recency effect in serial recall when the last item was made more distinct in terms of its color. In an attempt to extend this finding, three experiments were conducted in which visual distinctiveness was manipulated in a different manner, by combining the dimensions of physical size and coloration (i.e., whether the stimuli were solid or outlined in relief). Contrary to previous findings, recency was enhanced when the size and coloration of the last item differed from the other items in the list, regardless of whether the "distinctive" item was larger or smaller than the remaining items. The findings are considered in light of other research that has failed to obtain a similar enhanced recency effect, and their implications for current theories of the modality effect are discussed.