Unchained Memory: Error Patterns Rule out Chaining Models of Immediate Serial Recall

Many models of serial recall assume a chaining mechanism whereby each item associatively evokes the next in sequence. Chaining predicts that, when sequences comprise alternating confusable and non-confusable items, confusable items should increase the probability of errors in recall of following non-confusable items. Two experiments using visual presentation and one using vocalized presentation test this prediction and demonstrate that: (1) more errors occur in recall of confusable than alternated non-confusable items, revealing a 'sawtooth' in serial position curves; (2) the presence of confusable items often has no influence on recall of the non-confusable items; and (3) the confusability of items does not affect the type of errors that follow them. These results are inconsistent with the chaining hypothesis. Further analysis of errors shows that most transpositions occur over short distances (the locality constraint), confusable items tend to interchange (the similarity constraint), and repeated responses are rare and far apart (the repetition constraint). The complete pattern of errors presents problems for most current models of serial recall, whether or not they employ chaining. An alternative model is described that is consistent with these constraints and that simulates the detailed pattern of errors observed.