Testing feature interaction : Between stream irrelevant speech effects in immediate recall

Immediate serial recall of visually presented lists is disrupted by irrelevant background speech. One explanation for the irrelevant speech effect assumes that features of the auditory material become incorporated into the memory trace of the to-be-remembered item thereby reducing the fidelity of the short-term trace. From this perspective the resultant short-term memory trace is a composite of features of the list item and features of an item in the irrelevant stream. While there is evidence that item interactions in short-term memory are observable, there is currently no direct empirical evidence for such interactions involving irrelevant speech. We report six experiments using a short-term cued recall task that manipulates proactive interference in which item interactions have been observed. In these experiments we consistently show that with irrelevant speech specific items in the auditory stream influence target recall and the presence or absence of proactive interference. These results provide relatively direct evidence for feature interaction involving irrelevant speech. The results are evaluated against the three current models of irrelevant speech effects.