Spacing Effect

Features of the Spacing Effect

The spacing effect is well established in memory-dependent learning tasks and has been demonstrated most frequently using paired-associate and free-recall memory tasks. In a paired-associate spacing-effect experiment, pairs of words or other stimuli are associated over repeated practices that are spaced in time by practicing other item pairs during spacing intervals. Recall in paired-associate memory tasks may be tested at the conclusion of practice by prompting with one member of each pair to cue recall of the other pair member, but many experiments include a buffer task or a short-term or long-term interval (typically at least a day) between learning and retention, since a paired-associate spacing effect seems to require a significant retention interval to become apparent.

In a free-recall task, participants learn a word list in which some of the words repeat, again with spacing defined by the number of intervening items between repetitions. The effect of spaced practice of items in a list is determined with testing after the conclusion of practice, either immediately or with some retention delay interval. Spacing effects in free-recall lists are often apparent without the need for a significant retention interval.

While the spacing effect has been most thoroughly studied in memory tasks and might be expected to occur in any task with a memory component, it has also been reported in motor skill tasks. However, there has been much less research on the spacing effect in motor skill tasks, and it is still unclear to what extent spacing effects are universal to all types of learning. In fact, many researchers have proposed multiple mechanisms for spacing effects, and it is possible that spacing effects occur because of different mechanisms depending on the task.

The spacing effect often shows strong interactions with the amount of practice and the duration of the retention interval. The practice by spacing [Page 711]interaction is characterized by an increasing benefit from spacing as practices accumulate. This interaction means that additional spaced practices beyond the second trial will continue to contribute more learning if the practices are widely spaced. The spacing by retention interval interaction, which can only be detected using experiments with multiple retention intervals, is a tendency for much more rapid forgetting following practice that is narrowly spaced (i.e., the effect of spacing is greater after longer retention intervals).

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