Academic journal article Memory & Cognition

Output Order in Immediate Serial Recall

Academic journal article Memory & Cognition

Output Order in Immediate Serial Recall

Article excerpt

In two experiments, we examined the effect of output order in immediate serial recall (ISR). In Experiment 1, three groups of participants saw lists of eight words and wrote down the words in the rows corresponding to their serial positions in an eight-row response grid. One group was precued to respond in forward order, a second group was precued to respond in any order, and a third group was postcued for response order. There were significant effects of output order, but not of cue type. Relative to the forward output order, the free output order led to enhanced recency and diminished primacy, with superior performance for words output early in recall. These results were replicated in Experiment 2 using six-item lists, which further suggests that output order plays an important role in the primacy effect in ISR and that the recency items are most highly accessible at recall.

In the immediate serial recall (ISR) task, participants are presented with sequences of digits, letters, or words and, immediately after the last item has been presented, must try to recall as many of the items as possible in the correct serial order. With very short lists, performance on the task is near-perfect, but as the list length is increased, performance breaks down in a characteristic manner: There are extended primacy effects (superior recall of early items) and limited recency effects (superior recall of terminal items). These large primacy effects are rather distinctive, because performance in many other immediate memory tasks (such as sequential probed recall and cued recall) typically lead to recency-dominated serial position curves. The resulting serial position curve in ISR has become a fundamental empirical finding that must be explained by all models of ISR.

Primacy effects have been modeled in a number of different ways. Many models assume that the encoding or activation strength of successive list items decreases over serial positions, so that items in early input positions have greater activations than do subsequent items. In some models, this is the primary cause of primacy effects (e.g., Farrell & Lewandowsky, 2002; Lewandowsky, 1999; Page & Norris, 1998). For example, in Page and Norris's primacy model, the result of the greater activation of the earlier items is a primacy gradient. During recall, the most active item, usually the first presented item, is first chosen for recall and then suppressed. Following this, the item with the next highest activation is recalled and suppressed, and so on. The primacy gradient decays exponentially over time, and at recall, this produces a steep primacy effect.

In other models, item selection at recall is not based directly on the items' activation strengths, but indirectly through positional, temporal, or contextual markers (e.g., Brown, Preece, & Huhne, 2000; Burgess & Hitch, 1999; Henson, 1998). Nevertheless, many of these models similarly incorporate some form of primacy gradient. In Henson's start-end model (SEM ), for example, each item is stored in memory as a token containing information about the item's position relative to the start and end of a list. During retrieval, items are cued by reinstating the positional markers for each item and comparing the overlap in positional information between the cue and the tokens in memory. Primacy and recency effects are produced mainly because the positional markers have a greater positional distinctiveness at the start and end of a list. In addition, the start marker is more distinctive than the end marker, leading to a larger primacy than recency effect.

A third class of short-term memory model is based on the idea of the temporal or contextual distinctiveness of list items (Brown, Neath, & Chater, 2007; Glenberg & Swanson, 1986). In these models, items in memory are thought to be situated along a temporal or contextual continuum, and recall is considered to be a process of discrimination along this continuum. …

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