The effects of irrelevant speech and articulatory suppression on the serial recall of silently presented lipread digits

The immediate serial recall of lipread material is disrupted by irrelevant speech (Campbell & Dodd, 1984; Jones, 1994) and by articulatory suppression (Campbell & Dodd, 1984). However, the interaction between these has not be en directly examined. In Exp 1, participants recalled silently presented li pread digits in conditions of quiet, irrelevant speech, articulatory suppre ssion and suppression/speech combined. Irrelevant speech disrupted recall, but not when articulation was suppressed. Experiment 2 demonstrated that pa rticipants were able to accurately lipread targets in all of the above expe rimental conditions. A third experiment contrasted predictions derived from the phonological loop model (PL; Baddeley, 1986) and the changing state hy pothesis (CSH; Jones, 1993). The CSH predicts that tones and speech that va ry in frequency to the same degree will disrupt recall equally (Jones & Mac ken, 1993), whereas the PL model implies that speech will always be more di sruptive. The results support the CSH, and extend the findings of Jones and Macken (1993) to account for lipread stimuli. As with graphic presentation , the CSH provides a better account of the processes underpinning the irrel evant speech effect; however, it is argued that the recoding hypothesis fro m the PL model should be retained.