The testing effect is the finding that long-term memory is increased when some of the learning period is devoted to retrieving the to-be-remembered information through testing with proper feedback. The effect is also sometimes referred to as retrieval practice, practice testing, or test-enhanced learning.
It is useful for people to test their knowledge of the to-be-remembered material during the studying process, instead of solely studying or reading the material. For example, a student can use flashcards to self-test and receive feedback as they study. The testing effect provides the largest benefit to long-term memory when the tested material is difficult enough to require effort, the retrieval success is high, and feedback with correct answers is given after testing.
The first documented empirical study on the testing effect was published in 1917 by Gates. An important step in proving the existence of the testing effect was presented in a 1992 study by Carrier and Pashler. Carrier and Pashler showed that testing practice does not just provide an additional practice opportunity, but produces better results than other forms of studying. In their experiment, learners who tested their knowledge during practice later remembered more information than learners who spent the same amount of time studying the complete information. The abstract summarizes the results as follows:
In the pure study trial (pure ST condition) method, both items of a pair were presented simultaneously for study. In the test trial/study trial (TTST condition) method, subjects attempted to retrieve the response term during a period in which only the stimulus term was present (and the response term of the pair was presented after a 5-sec delay). Final retention of target items was tested with cued-recall tests. In Experiment 1, there was a reliable advantage in final testing for nonsense-syllable/number pairs in the TTST condition over pairs in the pure ST condition. In Experiment 2, the same result was obtained with Eskimo/English word pairs. This benefit of the TTST condition was not apparently different for final retrieval after 5 min or after 24 h. Experiments 3 and 4 ruled out two artifactual explanations of the TTST advantage observed in the first two experiments. Because performing a memory retrieval (TTST condition) led to better performance than pure study (pure ST condition), the results reject the hypothesis that a successful retrieval is beneficial only to the extent that it provides another study experience.
Carrier and Pashler study did not reveal a very large advantage of testing over studying, but paved the way for numerous further studies that have shown a more marked advantage. The results of a 2010 study by Agarwal et al. showed that the desirable difficulty of open-book and closed-book tests better enhanced learning compared to restudying or testing without feedback. Additionally, a study done by Roediger and Karpicke showed that students in the repeated-testing condition recalled much more after a week than did students in the repeated-study condition (61% vs. 40%), even though students in the former condition read the passage only 3.4 times and those in the latter condition read it 14.2 times. However, another study by Butler cites that testing only promotes the learning of a specific response, and his results showed that the mnemonic benefits of retrieving information from memory are seen well beyond this retention of a specific response. Thus, most studies show greater advantages for testing compared to studying or restudying as it relates to long-term retention of to-be-remembered information, but some studies have produced results that have contradicted this claim. Using retrieval practices also produces less forgetting than studying and restudying. Future research must consider the results and methods of both viewpoints in order to produce results that represent whether testing or studying has greater benefits on long-term retention of information.
In order for a testing effect to be demonstrated, the test trials must have a medium to high retrieval success. If the test trials are so difficult that no items are recalled, or if there is not proper feedback providing answers to the non-recalled items, then minimal information will be encoded and stored to memory.
Benefits of testing are often only visible after a delay and not immediately after practice, when outcomes may even be better for restudied materials than for tested materials. Some authors suggest that this can be explained in part by limited retrieval success during practice.
According to the retrieval effort hypothesis, "difficult but successful retrievals are better for memory than easier successful retrievals". For example, Pyc and Rawson showed that repeated testing is more beneficial for learning if the intervals between repeated testing are long and each test is therefore more difficult than when the intervals are short and tests are easy. This finding is related to the theory that certain conditions that make learning more effortful through so-called desirable difficulties are beneficial. Another finding showed that weaker cues for recalling information will be more beneficial to future recollection compared to that of stronger cues. Although these strong cues were shown to be more advantageous for initial recall, these stronger cues reduced the likelihood of activating more elaborative information that could be beneficial for retention. On the hand, the weak cues better allowed the to-be-remembered information to be better retained over time, enhancing long-term memory of the information.
Two views have arisen as to why testing seems to provide such a benefit over repeated study. The first view, provided by McDaniel, states that testing allows people to formulate newer, more lasting connections between items than does repeated study. The second view, provided by Karpicke and Roediger studied the effect of testing on memory retention. They found that re-studying or re-reading memorized information had no effect, but trying to recall the information had an effect. New findings show more support for the second view. Spacing has also been shown to improve memory in younger and older adults. The spacing effect improves long-term memory from learning material with a break in between learning other information, while the testing effect improves long-term memory by restudying learned information through testing. Both of these methods have been combined to be referred to as space retrieval practice.
Before much experimental evidence had been collected, the utility of testing was already evident to some perceptive observers. In his 1932 book Psychology of Study, C. A. Mace said "On the matter of sheer repetitive drill there is another principle of the highest importance: Active repetition is very much more effective than passive repetition. ... there are two ways of introducing further repetitions. We may re-read this list: this is passive repetition. We may recall it to mind without reference to the text before forgetting has begun: this is active repetition. It has been found that when acts of reading and acts of recall alternate, i.e., when every reading is followed by an attempt to recall the items, the efficiency of learning and retention is enormously enhanced." In other words, the testing effect shows that when material is reviewed, the reviewer actively challenges their memory to recall than when re-reading or re-studying the materials. This is called active recall.
Clearly the largest application for any human memory studies of learning effects is for education and finding better ways to relate information to students at every grade level. Extensive research has been done in this area in the last decade. With findings showing that the testing effect can have a greater impact after a delay even though students themselves seemed more confident in studying (which turned out to be false in the data). Additional reviews have sought to provide more reliable results of the testing effect to improve education, a trend that after nearly 100 years, seems to be catching on.