Recognition is identifying learned information using external cues. For example, true or false questions and multiple-choice questions test recognition because the previously learned information is there on the page, along with other options. In general, recognition is easier than recall.
When using the relearning method to measure retention, a researcher might ask a subject to memorize a long grocery list. She might measure how long he has to practice before he remembers every item. Suppose it takes him ten minutes. On another day, she gives him the same list again and measures how much time he takes to relearn the list. Suppose he now learns it in five minutes. He has saved five minutes of learning time, or 50 percent of the original time it took him to learn it. His savings score of 50 percent indicates that he retained 50 percent of the information he learned the first time.
Everyone forgets things. There are six main reasons for forgetting: ineffective encoding, decay, interference, retrieval failure, motivated forgetting, and physical injury or trauma.
The way information is encoded affects the ability to remember it. Processing information at a deeper level makes it harder to forget. If a student thinks about the meaning of the concepts in her textbook rather than just reading them, she’ll remember them better when the final exam comes around. If the information is not encoded properly—such as if the student simply skims over the textbook while paying more attention to the TV—it is more likely to be forgotten.
According to decay theory, memory fades with time. Decay explains the loss of memories from sensory and short-term memory. However, loss of long-term memories does not seem to depend on how much time has gone by since the information was learned. People might easily remember their first day in junior high school but completely forget what they learned in class last Tuesday.
Interference theory has a better account of why people lose long-term memories. According to this theory, people forget information because of interference from other learned information. There are two types of interference: retroactive and proactive.