Irrelevant speech effects and sequence learning.

The irrelevant speech effect is the finding that performance on serial recall tasks is impaired by the presence of irrelevant background speech. According to the object-oriented episodic record (O-OER) model, this impairment is due to a conflict of order information from two different sources: the seriation of the irrelevant speech and the rehearsal of the order of the to-be-remembered items. We tested the model's prediction that irrelevant speech should impair performance on other tasks that involve seriation. Experiments 1 and 2 verified that both an irrelevant speech effect and a changing state effect would obtain in a between-subjects design in which a standard serial recall measure was used, allowing employment of a between-subjects design in subsequent experiments. Experiment 3 showed that performance on a sequence-learning task was impaired by the presence of irrelevant speech, and Experiment 4 verified that performance is worse when the irrelevant speech changes more (the changing state effect). These findings support the prediction made by the O-OER model that one essential component to the irrelevant speech effect is serial order information.

Fill-in and infill errors in order memory.

Many current models of memory are specified with enough detail to make predictions about patterns of errors in memory tasks. However, there are often not enough empirical data available to test these predictions. We report two experiments that examine the relative frequency of fill-in and infill errors. In immediate serial recall tasks, subjects sometimes incorrectly recall item N too soon, placing it in position N-1. The error of interest is which item is recalled after this initial mistake. A fill-in error is the tendency to recall item N-1 next, whereas an infill error is the tendency to recall item N+1 next. Both experiments reveal more fill-in than infill errors, not only overall but at each possible error location throughout the list. The overall ratio is approximately 2:1. We conclude that none of the currently existing models adequately accounts for fill-in and infill errors.

Directly assessing the relationship between irrelevant speech and articulatory suppression.

Larsen and Baddeley (2003) examine whether the disruption caused by articulatory suppression on immediate memory tasks is similar to or different from the disruption caused by irrelevant speech. Based on experiments in which they test whether the phonological similarity effect is present or absent, they conclude that articulatory suppression and irrelevant speech are different. We assessed whether articulatory suppression and irrelevant speech are similar or different by correlating the disruption each causes. A significant correlation obtained, indicating a relation between the two. These apparently different conclusions can be readily resolved by adopting the view that articulatory suppression, irrelevant speech, and many other factors vary in the degree to which they are likely to cause subjects to abandon reliance on phonological/acoustic cues in particular tasks.