What can we learn about immediate memory from the development of children's free recall?

We ask the question: Which aspects of immediate memory performance improve with age? In two studies, we reexamine the widely held view that primary memory capacity estimates derived from children's immediate free recall are age invariant. This was done by assessing children's immediate free-recall accuracy while also measuring the order in which they elected to recall items (Experiment 1) and by encouraging children to begin free recall with items from towards the end of the presented list (Experiment 2). Across samples aged between 5 and 8 years we replicated the previously reported age-related changes in free-recall serial position functions when aggregated across all trials of the standard task, including an absence of age differences in the recency portion of this curve. However, we also show that this does not reflect the fact that primary memory capacity is constant across age. Instead, when we incorporate order of report information, clear age differences are evident in the recall of list-final items that are output at the start of a participant's response. In addition, the total amount that individuals recalled varied little across different types of free-recall tasks. These findings have clear implications for the use of immediate free recall as a means of providing potential indices of primary memory capacity and in the study of the development of immediate memory.

How does processing affect storage in working memory tasks? Evidence for both domain-general and domain-specific effects.

Two studies that examine whether the forgetting caused by the processing demands of working memory tasks is domain-general or domain-specific are presented. In each, separate groups of adult participants were asked to carry out either verbal or nonverbal operations on exactly the same processing materials while maintaining verbal storage items. The imposition of verbal processing tended to produce greater forgetting even though verbal processing operations took no longer to complete than did nonverbal processing operations. However, nonverbal processing did cause forgetting relative to baseline control conditions, and evidence from the timing of individuals' processing responses suggests that individuals in both processing groups slowed their responses in order to "refresh" the memoranda. Taken together the data suggest that processing has a domain-general effect on working memory performance by impeding refreshment of memoranda but can also cause effects that appear domain-specific and that result from either blocking of rehearsal or interference.

The nature and position of processing determines why forgetting occurs in working memory tasks.

The effect of potentially distracting processing within working memory was examined by varying the nature and position of processing across conditions of a Brown-Peterson-like task. Separate groups of participants carried out verbal or visuospatial processing operations on identical stimuli, while retaining lists of to-be-remembered words. The number of words presented either before or after the processing interval was varied systematically. Results showed that although verbal processing was no more demanding than visuospatial processing, it led to greater forgetting. However, forgetting was confined to items presented prior to processing, and the difference in degree of forgetting shown by the two groups was maximal when four items occurred before processing. Temporal isolation effects were more marked in the verbal processing group. These findings indicate that individuals can keep active a limited number of items in primary memory during processing, unless processing blocks rehearsal, in which case retrieval occurs from secondary memory.