Sources of Intratrial Interference in Immediate Recall of Paired Associates 1

A typical verbal-learning trial consists of two distinct phases, presentation of the material and attempted recall, or input and output. While many different patterns of input and output sequences can be and have been used in experiments, the two phases are necessarily separated in time. A reasonably small unit of material, such as an individual item, can practically always be recalled immediately after its presentation (Murdock, 1961a, b; Peterson, Saltzman, Hillner, and Land, 1962). In this sense the item is always "learned" when it is presented. If it cannot be recalled following a retention interval, however short, it must have been "forgotten" during that interval. This paper is concerned with intratrial forgetting of individual list items, i.e., with forgetting as it occurs within a single learning trial. Intratrial retention intervals of individual items are filled with inputs and outputs of other items. These two kinds of intervening activities can be regarded as two sources of intratrial interference responsible for forgetting of the critical item. If a list of, say, ten items A, B, C, . . . , I, J, is presented to S in this order and at a fixed rate, and S is then asked to recall these items in the same order and at the same rate, the length of the intratrial retention interval is identical for all items, but the particular combination of intervening inputs and outputs varies for items in different serial posi-