Search

The authors performed a meta-analysis of the distributed practice effect to illuminate the effects of temporal variables that have been neglected in previous reviews. This review found 839 assessments of distributed practice in 317 experiments located in 184 articles. Effects of spacing (consecutive massed presentations vs. spaced learning episodes) and lag (less spaced vs. more spaced learning episodes) were examined, as were expanding interstudy interval (ISI) effects. Analyses suggest that ISI and retention interval operate jointly to affect final-test retention; specifically, the ISI producing maximal retention increased as retention interval increased. Areas needing future research and theoretical implications are discussed., (Copyright 2006 APA, all rights reserved.)

Previous studies combining continuous free recall with a concurrent task have generally shown that concurrent tasks impose fairly negligible effects on memory retrieval. By contrast, dual-task studies employing either cued recall or semantic retrieval reveal gross memory impairment and suggest that retrieval is delayed by the centrally demanding phase of the concurrent tasks (i.e., response selection). To explore this conflict, subjects performed continuous free recall while carrying out a serial-choice-response time (RT) task, as in the previous free recall studies. Unlike these previous studies, however, the choice-RT task utilized arbitrary stimulus-response mappings in order to increase the proportion of time devoted to the centrally demanding response selection phase. Recall total was reduced significantly, and recall latency was slowed substantially.

The recall of previously studied items is widely believed to incorporate a search of a markedly constrained set of possibilities, and the present study examines whether this set of items typically includes unstudied semantic associates of the study items. In an episodic task, participants recalled a previously studied list of eight exemplars drawn from a small or large category, and, in a semantic task, participants generated exemplars from these categories. Category size affected the time course of recall in the semantic task but not in the episodic task. This empirical dissociation between episodic and semantic memory is consistent with the view that episodic memory search efficiently excludes unstudied semantic associates of the study items and is instead constrained to those items sharing the temporal and spatial attributes of the episode.

Subjects studied either an 8- or 16-word list and later recalled the items while a voice key recorded each response latency. The trials were partitioned by recall total in order to examine the means and distributions of both latencies and interresponse times as a function of recall total. Each analysis was consistent with the view that an item's absolute strength determines whether it is recalled whereas an item's relative strength determines when it is recalled. In addition, mean latency was effectively proportional to study list length yet independent of recall total. All of the analyses were consistent with the view that the set of study items is sampled according to a relative-strength rule until all items are found and that a sampled item is recovered into consciousness only when its absolute strength exceeds a fixed threshold.

In 3 experiments, participants generated category exemplars (e.g., kinds of fruits) while a voice key and computer recorded each response latency relative to the onset of responding. In Experiment 1, mean response latency was faster when participants generated exemplars from smaller categories, suggesting that smaller mental search sets result in faster mean latencies. In Experiment 2, a concurrent secondary task increased mean response latency, suggesting that slowed mental processing results in slower mean latencies. In Experiment 3, the mean response latency of Alzheimer's participants was faster than that of elderly controls, which is consistent with the idea that the semantic memory impairments of Alzheimer's disease patients stem primarily from a reduction in available items (as in Experiment 1) rather than retrieval slowing (as in Experiment 2).

In four experiments, subjects freely recalled previously studied items while a voice key and computer recorded each item's recall latency relative to the onset of the recall period. The measures of recall probability and mean recall latency were shown to be empirically independent, demonstrating that there exists no a priori relationship between the two. In all four experiments, latency distributions were fit well by the ex-Gaussian, suggesting that retrieval includes a brief normally distributed initiation stage followed by a longer exponentially distributed search stage. Further, the variation in mean latency stemmed from the variation in the duration of the search stage, not the initiation stage. Interresponse times (IRTs), the time elapsed between two successive item recalls, were analyzed as well. The growth of mean IRTs, plotted as a function of output position, was shown to be a simple function of the number of items not yet recalled. Finally, the mathematical nature of both free recall latency and IRT growth are shown to be consistent with a simple theoretical account of retrieval that depicts mean recall latency as a measure of the breadth of search.

In demonstrations of part-list cuing inhibition, subjects who are shown a subset of studied list words recall fewer noncue words than subjects not shown such part-list cues. We propose that part-list inhibition is governed in part by an incongruency principle: Inhibition occurs to the extent that part-list cues induce a retrieval framework different from that used to encode list items. In Experiment 1, word lists were studied followed by a test of free recall either without cues, or with cue words serially organized to be either congruent or incongruent with the order of studied items. In Experiments 2-4, cues consisted of every second study item in the original presentation order (congruent ones) or reordered to form famous names or familiar idioms that had been hidden in the study list (incongruent cues). More part-list inhibition was observed with incongruent cues than congruent cues in all 4 experiments.