Doug Rohrer

Distributed practice in verbal recall tasks: A review and quantitative synthesis

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.

When Does Feedback Facilitate Learning of Words

Some researchers have suggested that although feedback may enhance performance during associative learning, it does so at the expense of later retention. To examine this issue, subjects (N = 258) learned Luganda-English word pairs. After 2 initial exposures to the materials, subjects were tested on each item several times, with the presence and type of feedback varying between subjects. A final test followed after 1 week. Supplying the correct answer after an incorrect response not only improved performance during the initial learning session--it also increased final retention by 494%. On the other hand, feedback after correct responses made little difference either immediately or at a delay, regardless of whether the subject was confident in the response. Practical and theoretical implications are discussed.

Spacing Effects in Learning A Temporal Ridgeline of Optimal Retention

To achieve enduring retention, people must usually study information on multiple occasions. How does the timing of study events affect retention? Prior research has examined this issue only in a spotty fashion, usually with very short time intervals. In a study aimed at characterizing spacing effects over significant durations, more than 1,350 individuals were taught a set of facts and—after a gap of up to 3.5 months—given a review. A final test was administered at a further delay of up to 1 year. At any given test delay, an increase in the interstudy gap at first increased, and then gradually reduced, final test performance. The optimal gap increased as test delay increased. However, when measured as a proportion of test delay, the optimal gap declined from about 20 to 40% of a 1-week test delay to about 5 to 10% of a 1-year test delay. The interaction of gap and test delay implies that many educational practices are highly inefficient.

Analyzing the dynamics of free recall: An integrative review of the empirical literature

Relatively few experiments have measured the time course of free recall from episodic or semantic memory. Of those that have, most report that cumulative recall is a negatively accelerated exponential (or hyperbolic) function that is characterized by two properties: asymptotic recall and rate of approach to asymptote. The most common measure of free recall performance (viz., the number of items recalled) provides a reasonably good estimate of asymptotic recall if a relatively long recall period is used (which is rare), but the effect of experimental manipulations on the rate of approach to asymptote cannot be determined without timing when recall responses occur. The research reviewed herein suggests that the rate of approach to asymptote may offer an estimate of the breadth of search through long-term memory. The search in question, unlike most of those investigated in the memory literature, is unique in that it requires minutes rather than milliseconds to complete.

Recent Research on Human Learning Challenges Conventional Instructional Strategies

There has been a recent upsurge of interest in exploring how choices of methods and timing of instruction affect the rate and persistence of learning. The authors review three lines of experimentation—all conducted using educationally relevant materials and time intervals—that call into question important aspects of common instructional practices. First, research reveals that testing, although typically used merely as an assessment device, directly potentiates learning and does so more effectively than other modes of study. Second, recent analysis of the temporal dynamics of learning show that learning is most durable when study time is distributed over much greater periods of time than is customary in educational settings. Third, the interleaving of different types of practice problems (which is quite rare in math and science texts) markedly improves learning. The authors conclude by discussing the frequently observed dissociation between people’s perceptions of which learning procedures are most effective and which procedures actually promote durable learning.

Enhancing learning and retarding forgetting: choices and consequences.

Our research on learning enhancement has been focusing on the consequences for learning and forgetting of some of the more obvious and concrete choices that arise in instruction, including questions such as these: How does spacing of practice affect retention of information over significant retention intervals (up to 1 year)? Do spacing effects generalize beyond recall of verbal materials? Is feedback needed to promote learning, and must it be immediate? Although retrieval practice has been found to enhance learning in comparison with additional study, does it actually reduce the rate of forgetting? Can retrieval practice effects be extended to nonverbal materials? We suggest that as we begin to find answers to these questions, it should become possible for cognitive psychology to offer nonobvious advice that can be applied in a variety of instructional contexts to facilitate learning and reduce forgetting.

Tests enhance the transfer of learning

Numerous learning studies have shown that if the period of time devoted to studying information (e.g., casa-house) includes at least 1 test (casa-?), performance on a final test is improved-a finding known as the testing effect. In most of these studies, however, the final test is identical to the initial test. If the final test requires a novel demonstration of learning (i.e., transfer), prior studies suggest that a greater degree of transfer reduces the size of the testing effect. The authors tested this conjecture. In 2 experiments, 4th- or 5th-grade students learned to assign regions or cities to map locations and returned 1 day later for 2 kinds of final tests. One final test required exactly the same task seen during the learning session, and the other final test consisted of novel, more challenging questions. In both experiments, testing effects were found for both kinds of final tests, and the testing effect was no smaller, and actually slightly larger, for the final test requiring transfer. (PsycINFO Database Record (c) 2009 APA, all rights reserved).

Optimizing Distributed Practice Theoretical Analysis and Practical Implications

More than a century of research shows that increasing the gap between study episodes using the same material can enhance retention, yet little is known about how this so-called distributed practice effect unfolds over nontrivial periods. In two three-session laboratory studies, we examined the effects of gap on retention of foreign vocabulary, facts, and names of visual objects, with test delays up to 6 months. An optimal gap improved final recall by up to 150%. Both studies demonstrated nonmonotonic gap effects: Increases in gap caused test accuracy to initially sharply increase and then gradually decline. These results provide new constraints on theories of spacing and confirm the importance of cumulative reviews to promote retention over meaningful time periods.

An analysis of latency and interresponse time in free recall.

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.

proactive interference and the dynamics of free recall

Proactive interference (PI) has long been recognized as a major cause of forgetting. We conducted two experiments that offer another look at the subject by providing a detailed analysis of recall latency distributions during the buildup of and release from PI. These functions were accurately characterized by the convolution of the normal and exponential distributions (viz., the ex-Gaussian), which previously has been shown to describe recognition latency distributions. Further, the fits revealed that the increase in recall latency associated with the buildup of PI results from a slowing of the exponential retrieval stage only. The same result was found even when a short retention interval was used (and recall probability remained constant). These findings suggest that free-recall latency may be a sensitive index of the increased search set size that has often been assumed to accompany the buildup of PI. A central insight emerging from the memory literature of the 1950s and 1960s was that previously learned information can result in the rapid forgetting of more recently learned information. Underwood (1957) argued that this phenomenon, termed proactive interference (PI), was by far the major cause of forgetting in everyday life. Indeed, even in laboratory experiments, the degree of retroactive interference encountered over the course of hours or days was assumed to pale in comparison with the degree of proactive interference resulting from years of prior learning. Although its preeminent (and still unexplained) role in the process of forgetting continues to be recognized, interest in the subject of PI has waned in recent years. The present article contributes a new empirical analysis of this important subject and pursues a detailed theoretical exploration into its underlying nature. In a typical PI experiment, subjects receive blocks of Brown-Peterson trials involving words from a single category (Wickens, 1972). Within a block, free-recall performance declines with each successive trial (the buildup of PI) but recovers each time a new category is introduced (release from PI). In most cases, the dependent variable used in these experiments was the percentage of correct free-recall responses. However, in the research to be presented here, we focus on latency to free recall. Research on free-recall latency in any context is very limited, and in the study of PI it is almost nonexistent. Why might free-recall latency be an interesting variable to investigate? Because such a measure provides important information about the process of retrieval that is likely to be missed by static measures, such as probability of recall. Before addressing the question of exactly what that information might be, we review the scant literature pertaining to the more general and purely empirical question of whether these