Discoveries in Learning and Forgetting

UCLA’s Robert Bjork is a leader in applying cognitive scientific discoveries to actual learning practises. Parents and coaches who help to shape the landscape of a Dangerous Child’s learning environment will benefit from a better understanding of the mental mechanisms of learning, as research moves forward.

Here are some excerpts from Robert Bjork’s research, with some links included for further research:

Applying Cognitive Psychology to Enhance Educational Practice

Testing effect

Taking a test often does more than assess knowledge; tests can also provide opportunities for learning. When information is successfully retrieved from memory, its representation in memory is changed such that it becomes more recallable in the future (e.g., R. A. Bjork, 1975); and this improvement is often greater than the benefit resulting from additional study (Roediger & Karpicke, 2006).

Most of us are familiar with the “pre-test / post-test” approach to continuing education. The pre-test functions as an “alerting mechanism” to salient information that will appear in the coming lecture or other learning exposure. The post-test then puts a cap on what was learned — but it also acts as a “prime” for further learning.

New Theory of Disuse

Sometimes people cannot access information that was well learned earlier (e.g., the address of the house where they grew up). And students find that although they can recall information over and over again the day before a test, they cannot always recall it at the time of examination. Finally, sometimes people cannot recall information at one point in time, but can recall it later. In looking at these situations, it seems that our memories work in strange and unpredictable ways. The function of our memories, however, may be predictable. The New Theory of Disuse (R. A. Bjork & E. L. Bjork, 1992) posits that there are two indices of memory strength: storage strength (SS) and retrieval strength (RS). Storage strength is how well learned something is; retrieval strength is how accessible (or retrievable) something is. To illustrate, imagine four possible situations. If something is well learned (e.g., the address where you have lived for several years), it has both high SS and high RS: You know it well and can retrieve it readily. The address of a friend that you visited for the first time this afternoon, however, may only have high RS (and low SS) because the address, although practiced recently, was not well learned. Thus, although you know the address now, you will be unlikely to be able to recall it in a few days because RS will decrease over time, especially for information with low SS. Sometimes information has high SS (due to it having been well learned), but cannot be retrieved (e.g., the address where you lived as a child). If you were provided with this address again, however, you would have the feeling that that information was somewhere in the recesses of your memory, and in fact, you would be likely to relearn it very quickly. Finally, information can have both low RS and low SS. This information would include things that you heard in class earlier today, but did not learn well and cannot recall now.

We are often told that the brain retains everything that was ever learned. The challenge is in the act of recalling what we have learned. Most of the applications discussed by Bjork have to do with a more refined training of recall.

Introduction to Desirable Difficulties

Imagine a scenario in which a teacher has students practice different examples of a single type of math problem for an hour in class. By the end of the hour, it may seem—both to the teacher and to the students—that this type of math problem has been mastered. On a test two weeks later, however, the benefit may not be evident. In fact, much to the dismay of the teacher and the students, performance during training is not always representative of long-term learning.

In contrast to the story told above, in which an easy training method was followed by poor performance later, imagine that the teacher had interleaved many different types of problems during in-class training drills. Recent research reveals that difficult training of this type produces higher scores on the test than the easier version described above (Rohrer & Taylor, 2007), and this is the kind of training that the Bjork Learning and Forgetting Lab believes enhances long-term learning.

There are, in fact, certain training conditions that are difficult and appear to impede performance during training but that yield greater long-term benefits than their easier training counterparts.

Dr. Bjork explains that it is beneficial to create study conditions in which learning is slowed down to allow for better memory for the information in the long-term. This creates an unfortunate conflict between the desire to see quick improvements on the side of the learner and the instructional goals of the instructor.

An interesting real world example of “desirable difficulties” in learning was the method that the father of golf champion Tiger Woods used to train young Tiger in overcoming distractions. The father and coach would stand close to Tiger while the boy was trying to achieve a difficult putt, and shout in his ear. Using such distractions and other created difficulties, young Tiger was taught to focus intensely and to ignore the extraneous.


It is common sense that when we want to learn information, we study that information multiple times. The schedules by which we space repetitions can make a huge difference, however, in how well we learn and retain information we study. The spacing effect is the finding that information that is presented repeatedly over spaced intervals is learned much better than information that is repeated without intervals (i.e., massed presentation). This effect is one of the most robust results in all of cognitive psychology and has been shown to be effective over a large range of stimuli and retention intervals from nonsense syllables (Ebbinghaus, 1885) to foreign language learning across many months (Bahrick, Bahrick, Bahrick & Bahrick, 1993).

One of many approaches to spaced practise


One robust and longstanding finding is that generating words, rather than simply reading them, makes them more memorable (Slamecka & Graf, 1978). As an example, this effect is often achieved for single words through the use of a letter-stem cue (ex. “fl____” for “flower”) or by unscrambling an anagram (ex. “rolwfe” for “flower”). The effects of generation on memory are being investigated from many different angles in the lab, from its basic role as a memory modifier (see Desirable Difficulties), to people’s awareness of this role and subsequent use of generation as a strategy (see Metacognition), to the extended effects of generation on related material (see Retrieval-Induced Forgetting).

This approach is a giant step beyond the multiple choice approach, toward a more genuine fluency in knowledge and problem solving. Multiple choice testing and learning provides good introductions and intermediate learning experiences, while “generation” approaches allow for a closer approach to mastery.


Spacing is one of the most robust, effective ways of improving learning. However, spacing calls for intervals of time in between repetitions, and this may not be the most efficient use of time. Imagine you have three final exams to study for. If you were to space out study of three whole courses, you might as well start your course review before the quarter even begins! Particularly when one has several different things to learn, an effective strategy is to interleave one’s study: Study a little bit of history, then a little bit of psychology followed by a chapter of statistics and go back again to history. Repeat (best if in a blocked-randomized order).

The benefit of interleaving is found over a diverse set of stimuli ranging from word pairs (Battig, 1979) to motor movements (Shea & Morgan, 1979) to mathematics problems (Rohrer & Taylor, 2007) and word translations (Richland, R. A. Bjork, & Finley, 2004). Interleaving benefits not only memory for what is studied, but also leads to benefits in the transfer of learned skills (e.g. Carson & Wiegand, 1979). The theory is that interleaving requires learners to constantly “reload” motor programs (in the case of motor skills) or retrieve strategies/information (in the case of cognitive skills) and allows learners to extract more general rules that aid transfer.

Interleaving forces the learning mind out of restricted cubby-holes so that it can make connections and distinctions between concepts and actions. It represents a more dynamic approach to learning which is analogous on a smaller scale to the concept of inter-disciplinary learning and working on a larger scale.

More from UCLA’s Bjorklab

Robert Bjork videos on long-term learning

More videos

Forgetting as a friend of learning — a Harvard talk by Robert Bjork:


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