The brain’s capacity to remember remains one of the least understood areas of science. What is understood is that memory is a process that occurs constantly and in varying stages. The memory process occurs in three stages: encoding, storage, and retrieval. Conditions present during each of these stages affect the quality of the memory, and breakdowns at any of these points can cause memory failure. The first stage, encoding, is the reception by the brain of some physical input that is changed into a form that the memory accepts. When a person is introduced to someone new, for example, that person’s name becomes a part of memory. Before information can be encoded, it first must be recognized and noted by the recipient. During the second stage, storage, learned facts or experiences are retained in either short-term or long term memory. In the third, or retrieval, stage, memory allows the previously learned facts or experiences to be recalled. Each of these stages plays an important role in both short-term and long-term memory, although it is believed they work differently depending on which memory is used.
As the term implies, short-term memory is used for items that need recall over short periods of time, sometimes as little as seconds. It is believed that short-term memories are encoded either visually or acoustically. Visual encoding is primary for recalling faces, places, and other visual experiences, while acoustic encoding is most important for verbal material. After looking up a number in a telephone book, for example, most people repeat the number to themselves several times before dialing the number. Rather than visualizing the written form of the numbers, the sound of the words becomes the means for recall. Experiments have demonstrated the importance of acoustic coding in the ability to recall lists of words or letters as well. When subjects were asked to recall a sequence of letters, those who made errors replaced the correct letter with a similarly sounding letter, for example ‘D’ instead of ‘T.’ Adequate operation of short-term memory is crucial when performing such everyday activities as reading or conversing. However, the capacity of short-term memory is quite limited. Studies have shown consistently that there is room in short-term memory for an average of seven items, plus or minus two (known as magic number seven). In experiments in which subjects are asked to recall a series of unrelated numbers or words, for example, some are able to recall nine and others only five, but most will recall seven words. As the list of things to be remembered increases, new items can displace previous items in the current list.
Memory uses a process called ‘chunking’ to increase the capacity of short-term memory. While most people still can use only seven ‘slots’ of memory, facts or information can be grouped in meaningful ways to form a chunk of memory. These chunks of related items then act as one item within short-term memory. Long-term memory contains information that has been stored for longer periods of time, ranging from a few minutes to a lifetime. When translating information for long-term memory, the brain uses meaning as a primary method for encoding. When attempting to recall a list of unrelated words, for instance, subjects often try to link the words in a sentence. The more the meaning of the information is elaborated, the more it will be recalled.
Voices, odors, and tastes also are stored in long term memory, which indicates that other means of encoding besides meaning are also used. Items are regularly transferred back and forth from short-term to long term memory. For example, rehearsing facts can transfer short-term memory into long-term. The chunking process in long-term memory can increase the capacity of short-term memory when various chunks of information are called upon to be used.
The breakdown in the retrieval of information from either memory can be the result of various factors, including interference, decay, or storage problems. In addition, researchers believe it is unlikely that all experiences or facts are stored in memory and thus are available for retrieval. Emotional factors, including anxiety, also contribute to memory failure in certain situations. Test anxiety, for example, may cause a student to forget factual information despite how well it has been learned. Amnesia, a partial or total loss of memory, may be caused by stroke, injury to the brain, surgery, alcohol dependence, encephalitis, and electroconvulsive therapy (ECT).
Many methods can be used to improve memory. Long-term memory may be improved using mnemonic,
or memory-aiding, systems. One, the ‘method of loci’ system, encourages an association between various images and unrelated words. The ‘key word’ method of learning a foreign language links the pronunciation of a new word with a picture that corresponds to the sound of the word. Context is another powerful memory aid that recognizes that people recall more easily facts or events more easily if they are placed in the same environment in which they learned them. For example, a person is more likely to recall specific memories from high school if they go to the school and retrace their paths. Imposing a meaningful organization on an unrelated group of facts or words also improves memory. The
EGBDF notes that represent the lines on a musical staff often are recalled using the sentence, ‘Every good boy does fine.’ The sentence has nothing to do with music; rather, it places a meaning on letters that, at first glance, seem random. Another notable mnemonic system, the PQRST method, is helpful in assisting students learn textbook material. The letters correspond to the five steps of the method: preview, question, read, self-recitation and test.
Questions of the reliability and fragility of memory have surrounded the controversy of false and recovered memory that surface under questioning primarily by psychotherapists. As lawsuits based upon recovered memory have been filed against adults accused of molesting children and in at least one case, the death of a childhood friend, recovered memories have come under scrutiny and questions raised about the validity, especially when memory has been recovered under coaching. The emotional state of either low points, such as boredom or sleepiness or high points, such as stress or trauma, decrease the accuracy of memory.