Modelling the disruptive effects of irrelevant speech on order information

The feature model (Nairne, 1990) is extended to include order information by incorporating aspects of Estes' (1972, 1997) perturbation theory. Order information is encoded with other cues in primary memory and precision is gradually lost due to drift along the appropriate dimension. Recall begins with the cue whose positional uncertainty gradient indicates it was in the first position with the highest probability. Order errors occur primarily because cues can "perturb" to adjacent positions: Although the appropriate secondary memory target is sampled, it is sampled out of order. However, cues that have not perturbed can also sample an incorrect secondary memory item, which is then recalled out of order. Thus, both order errors and item errors can give rise to recalling an item from the list in an incorrect position. A simulation shows that with the addition of the perturbation mechanism, the feature model can produce the appropriate order error gradients for short and long words recalled in quiet, accompanied by irrelevant speech, or accompanied by articulatory suppression.