244Tests are commonly used in educational settings as a means of assessing the state of a student's knowledge. Research has shown, however, that tests do much more than measure learning; they also enhance learning (e.g., Bjork, 1975Bjork, , 1988Carrier & Pashler, 1992;Glover, 1989;Hogan & Kintsch, 1971;McDaniel & Masson, 1985;Roediger & Karpicke, 2006b;Spitzer, 1939;Tulving, 1967;Wheeler & Roediger, 1992). Not only does information that has been tested become more recallable in the future than it would have been otherwise, that information, if retrieved, becomes more recallable than if such a test was replaced by an additional study opportunity. Testing as pedagogy, therefore, versus as assessment, seems to have great potential for application in training and educational contexts (see, e.g., Bjork, 1994a;Roediger & Karpicke, 2006a).An important aspect of tests as learning events is that the deeper, more difficult, and more complex retrieval is, the more powerful that retrieval will be in facilitating successful retrievals in the future (e.g., Bjork, 1975;Whitten & Bjork, 1977). Tests that require learners to engage in deep and elaborative retrieval processes are likely to be highly effective; tests that require only superficial processing-such as, in the limit, retrieving very recent information from short-term memory-are not. One simple way of making tests more difficult-and therefore inducing a deeper level of processing-is by delaying the time between learning and test. When tests are given immediately, learners are able to access information from memory in a way that affords little or no benefit above and beyond simply having such information re-presented to them or even beyond not having the information tested or re-presented. When tests are delayed, however, and the tobe-tested information has become less accessible, learners are forced to engage in the type of processing that promotes learning and long-term retention (e.g., Cull, 2000;Glover, 1989;Jacoby, 1978;Modigliani, 1976;Roediger & Karpicke, 2006b;Whitten & Bjork, 1977). Said differently, delayed tests constitute better practice for later recall because they exercise more of the processes needed to succeed on a later test (for an embellishment of that argument, see Bjork, 1988).With the benefit of a delayed test, however, also comes a potential danger. In order for an item to profit from being tested, the learner must be able to successfully retrieve that item from memory, and the likelihood of doing so decreases with the delay between learning and test. Thus, there is a dilemma: If the delay between learning and test is short, retrieval is likely to succeed but to be ineffectual; if the delay is long, retrieval is unlikely to succeed and, hence, also to be ineffectual. One potential way of dealing with this dilemma is by implementing an expanding schedule of tests. In order to ensure successful retrieval, initial tests should be relatively immediate, and then, as the to-be-learned information gains strength in memory, University of California, Los...

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