Short-term Memory for Repeated and Non-repeated Items

Abstract

Digit sequences containing repeated items are retained differently in short-term memory from sequences containing no repeated items. The repeated items are remembered better or worse than items in the corresponding positions of “all-different” sequences depending on the number of times the item is repeated, the number of items repeated, the number of items intervening between the occurences of a repeated item, and the position of the repeated items in relation to the beginning and end of the sequence. In every type of repetition studied, except one, memory for the non-repeated items in sequences with repeated items is better than for the corresponding items of all-different sequences. This is true in some cases despite significant specific interference between the (non-repeated) items following the separated occurrences of repeated items. The negative effects in memory for repeated items and the positive effects in memory for non-repeated items are greater when the items are presented at the rate of five per sec. than at one per sec., contrary to the hypothesis that differential rehearsal is responsible for these effects. The results are interpreted as supporting an “associative,” as opposed to a “non-associative,” theory of short-term memory, as this distinction is defined in the paper.