Interleaving Helps Students Distinguish among Similar Concepts

When students encounter a set of concepts (or terms or principles) that are similar in some way, they often confuse one with another. For instance, they might mistake one word for another word with a similar spelling (e.g., allusion instead of illusion) or choose the wrong strategy for a mathematics problem because it resembles a different kind of problem. By one proposition explored in this review, these kinds of errors occur more frequently when all exposures to one of the concepts are grouped together. For instance, in most middle school science texts, the questions in each assignment are devoted to the same concept, and this blocking of exposures ensures that students need not learn to distinguish between two similar concepts. In an alternative approach described in this review, exposures to each concept are interleaved with exposures to other concepts, so that a question on one concept is followed by a question on a different concept. In a number of experiments that have compared interleaving and blocking, interleaving produced better scores on final tests of learning. The evidence is limited, though, and ecologically valid studies are needed. Still, a prudent reading of the data suggests that at least a portion of the exposures should be interleaved

Dissociating early- and late-selection processes in recall: the mixed blessing of categorized study lists

Two experiments are reported in which we used type-2 signal detection theory to separate the effects of semantic categorization on early- and late-selection processes in free and cued recall. In Experiment 1, participants studied cue–target pairs for which the targets belonged to two, six, or 24 semantic categories, and later the participants were required to recall the targets either with (cued recall) or without (free recall) the studied cues. A confidence rating and a report decision were also required, so that we could compute both forced-report quantity and metacognitive resolution (type-2 discrimination), which served as our estimates of early- and late-selection processes, respectively. Consistent with prior research, having fewer categories enhanced the early-selection process (in performance, two > six > 24 categories). However, in contrast, the late-selection process was impaired (24 > six = two categories). In Experiment 2, encoding of paired associates, for which the targets belonged to either two or 20 semantic categories, was manipulated by having participants either form interactive images or engage in rote repetition. Having fewer categories again was associated with enhanced early selection (two > 20 categories); this effect was greater for rote repetition than for interactive imagery, and greater for free recall than for cued recall. However, late selection again showed the opposite pattern (20 > two categories), even with interactive-imagery encoding, which formed distinctive, individuated memory traces. The results are discussed in terms of early- and late-selection processes in retrieval, as well as overt versus covert recognition

The exemplar interleaving effect in inductive learning: moderation by the difficulty of category discriminations

Recent research demonstrates a spacing effect in inductive learning. Spacing different individual exemplars apart in time, rather than massing them together, aids in the learning of categories. Experiment 1 examined whether it is interleaving or temporal spacing that is critical to the spacing effect in the situation wherethe memory load is high, and the results favored interleaving. Experiment 2 examined the effect of the difficulty of the category discrimination on presentation style (massed vs. spaced) in inductive learning, and the results demonstrated that spacing (i.e., interleaving of exemplars from different categories) is advantageous for low-discriminabilty categories, whereas massing is more effective for high-discriminability categories. In contrast to these performance measures, massing was judged by participants to be more effective than spacing in both discriminability conditions, even when performance for low-discriminability categories showed the opposite