The testing effect is a psychological phenomenon that refers to an enhancement in the long-term retention of information as a result of taking a memory test.  However, in order for this effect to be demonstrated the test trials must have a medium to high retrieval success. Logically if the test trials are so difficult that no items are recalled or if the correct answers to the non-recalled items are not given to the test subject, then minimal or no learning will occur. This is by no means a new concept in the field of human memory, with the first documented empirical study occurring in 1917 by Gates. The effect is also sometimes referred to as retrieval practice or test-enhanced learning.

An important step in proving the existence of the testing effect as a function of the retrieval itself rather than simply a benefit of an additional study period was presented in a 1992 study by Carrier and Pashler. Carrier and Pashler proposed in their abstract that “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.” This groundbreaking study did not in fact reveal a very large advantage of testing over studying, but paved the way for future studies that have shown a more marked advantage.

Two conflicting views have arisen as to why testing seems to provide such a benefit over simply repeated studying. The first view provided by McDaniel defended the idea that testing better allows people to formulate newer, more copious lasting connections between items as opposed to simply restudying the same connections over and over. The second view stems from Roediger and Karpicke which basically states that when people encode associations between items, they are also encoding the process to retrieve those items and testing provides practice in activating these retrievals whereas studying could not. However, new findings have demonstrated more support of this second view when comparing the two ideas head-to-head.