Charting the trajectory of forgetting: Insights from a working memory period paradigm.

Working memory capacity is commonly measured in terms of its item span, and much less often in terms of its time span, or "period." The former measures how many items can be stored in working memory when carrying out episodes of concurrent processing. The latter complements this by determining the duration of processing episodes that can be tolerated while successfully storing a fixed number of items. We investigated the generality of previous evidence that working memory period varies with the distribution of longer and shorter processing episodes within a trial, and that notwithstanding such differences, a global measure of period is a reliable predictor of children's educational attainment. We describe data from 184 children, between 7 and 11 years of age, who completed variants of an operation period task with different distributions of processing episodes together with measures of scholastic attainment. Individual differences in period scores were consistent over two test sessions, and were predictive of reading and number skills. We replicated previous effects of the order of longer and shorter processing episodes, but found that they did not generalize fully to other manipulations of order. The results point to the contribution of subtle within-trial sequence configurations for working memory. We make the case for a broader view of what constrains working memory than exists in current models.