It is clear that S.T.M is a fragile store from which information can be quickly or easily lost. The precise mechanism for forgetting is unclear but it seems likely that interference, displacement and decay all have a major role to play.
Forgetting in Long Term Memory
Cell assemblies that house our memories located in L.T.M can sometimes decay without occasional rehearsal. Motor skills that require a continuous series of movements like swimming or riding a bike are resistant to decay whereas memory for some soft spoken or briefly exposed, irrelevant material is more likely to get lost.]
Decay
We have already seen that memories transferred to the L.T.M are fairly long lasting and stable. However that does not stop us from failing to remember things. This has led some psychologists to argue that decay can occur in L.T.M in the form of disuse.
The idea is that knowledge or skills that have not been used in a long time eventually fade away. However skills requiring motor skills do not seem to be forgotten even if not used in a long time.
Fleischman and Parker (1962) found that people who trained to fly using a flight simulator lost none of their skills over a 9 – 24 month period. However, McKenna and Glendon (1985) studied 215 shop and office workers who had volunteered to learn cardiac resuscitation. Measures of performance were taken over a three-month to three-year period. Performance dropped sharply on the measures after three months and declined to extremely low levels after 3 years. Baddeley (1999) suggests that flying a plane or riding a bike involves a continuous skill as each action provides a cue for the next action. Skills such as resuscitation are more complex and require accurate knowledge as well as motor skills. According to Baddeley these need continually refreshing if they are to be maintained.
There is further evidence to suggest that verbal memories are remarkably resistant to long-term decay. Bahrick and Phelps (1987) found that American college graduates showed rapid forgetting of Spanish vocabulary over the first three to four years but showed little decline after this for the following 30 to 50 years. All this shows that even when time plays an important role forgetting it cannot be the only factor.
Interference
The interference theory is based on the behaviourist’s view that memory consists of associations made between specific stimuli and responses. It was a view put forward in the 1950’s but by the end of the 1960’s behaviourism was not widely believed to be making any relevant contribution to cognitive psychology. A distinction has been made between to types of interference
- Retroactive Interference which occurs when new information interferes with existing information.
- Proactive Interference which occurs when old memory interferes with new information coming in
Firstly however we must address the problems that occur when separating the effects of time and interference. Baddeley and Hitch (1977) conducted a survey whereby they asked rugby players to recall the names of teams they had played against during the previous season. Due to illness and injury some of the players had been unable to play in all the fixtures. This meant for some of the players two games back meant two weeks ago whereas with others two games back meant four or five weeks ago. The findings showed that passage of time was not the main factor that determined how well the teams could be recalled, but it was the number of games that effected recall. In other words forgetting occurred more often where team members had other games interfere with previous fixtures rather than trace decay.
If interference is the major cause of forgetting within L.T.M it should be true that people will remember material over a time period providing no interfering material intervenes. It is clearly difficult to set up a condition whereby no participant is immobilized after learning with any opportunity for the occurrence of any new learning. This has led researchers to look at the effect of different types of interfering material on recall.
McGeoch and McDonald (1931) asked participants to learn and relearn lists of adjectives and then compared their performance on recall tests after interpolated tasks. Forgetting these adjectives was at its least when participants simply had to rest during the learning and recall and increased when participants were required to learn nonsense syllables in the interval. Rates were even higher when it was adjectives that were learned in the interval and were at there highest when the adjectives learned were similar in meaning to the original list. This shows that forgetting increases as a function of the similarity of the interfering material.
Retroactive Interference
Proactive Interference
Retrieval Failure
This is also known as the “tip-of-the-tongue” phenomenon and comes about when we think we know something but cannot recall it at that precise moment in time. This is due to the fact that the correct retrieval cues are not available. Sometimes different words related to the original memory can prompt us to remember the memory and these are called “interlopers.”
Brown (1991) has reviewed this phenomenon for the last 25 years and has concluded that people can correctly name the first letter of the target word between 50 and 70 per cent of the time along with being correctly accurate with the number of syllables in the word. The interloper theory (retrieval cue) was investigated by Perfect and Hanley (1992) who found that distinctiveness of the target word and its similarity in meaning play a factor in recall.
Tulving was another researcher to investigate retrieval cues and it was his work with Osler (1968) that led to some interesting findings. They presented participants with lists of words, each paired off with a weakly associated cue word e.g. city-dirty. Participants where then tested for free recall (without the cue word) or were cued with the word e.g. dirty. They found that cued recall consistently produced higher levels of recall. To counteract the argument that any semantic association might aid the recall, they gave participants weak semantic associates which were different to that of the original cue words. These cues did not aid in recall and so led them to conclude that specific retrieval cues aid recall if and only if the information is stored at the same time as the information about the membership of the word in a given list. While Tulving stressed the importance of cues at the encoding stage he later admitted that cues not present at this stage could also be helpful under certain circumstances.
Context Dependant and State Dependant Learning
Research has shown that we remember more if we recall things in the same state as what we learned them in. In other words how we encode material at the time of learning is clearly important. Godden and Baddeley (1975) presented deep-sea divers with lists of words to learn. They learned these on the beach and under 15 feet of water. Recall was then tested in either the same or the opposite environment. Findings showed that recall was significantly better if tested in the same environment. These differences however are only small but it has been suggested that by even simply imagining the original environment can be helpful. Smith (1979) gave participants a list of 80 words to learn while sitting in a distinctive basement room. The following day he tested some of the participants on recall in the basement room and others in a fifth floor room with quite different surroundings. Average recall for the basement group was 18 but for those in the fifth floor room it was only 12. A third group was tested in the fifth floor room but were instructed to imagine themselves in the basement. The average recall for this was 17 words.
There is also some evidence to suggest that not only external environment plays a role in recall but also our internal environment i.e. physiological state or mood may play a part. Godwin et al (1969) found that heavy drinkers who learn things in a drunken state are more likely to recall them in a similar state. Eich (1980) has found similar findings with a range of drugs including marijuana.
Research into the Role of Emotional Factors in Forgetting
Flashbulb Memories
Psychologists have often ignored the role of emotion in human cognitive processes
but it seems likely that the way we feel has an impact upon the way we remember
things and one particular type of memory that seems to be influenced by emotion have been called flashbulb memories. This is a particularly vivid, detailed and long lasting memory of an event that is usually highly significant and emotional and is usually unexpected. It can be a personal event or something that provokes worldwide interest e.g. death of Princess Diana.
Research carried out by Brown and Kulik has led them to conclude that the event must be surprising and have real consequences for the person’s life. They believe that such an emotional event triggers a neural mechanism that causes details of the scene to be imprinted on the memory. They believe it is a special type of memory because the detail and accuracy with which the event is remembered and the fact that the structural form of the memory is always so similar. They believe six different types of information about the event are stored being
- Where they were
- What they were doing
- The person who gave them the news
- What they felt about it
- What others felt about it
- What happened in the immediate aftermath
However not all psychologists believe that flashbulb memories are special. Neisser (1982) believes that the longitivity of such memories result from frequent rehearsal and reworking of the event rather from neural activity at that precise moment in time. He believed that we recall it clearly due to the fact that we resort to storytelling techniques when telling someone about the event. It is still unclear whether flashbulb memories represent a particular type of memory or whether they are substantially similar to most memories for big events.
Repression
Another view about the way in which we forget things was put forward by Freud (1915-18) who believed that some memories become inaccessible as a result of repression. He believed that we use an unconscious process that ensures that threatening or anxiety-provoking memories are kept from our conscious awareness. These memories may stay repressed for years and never come to mind or can do in the form of hysterical neurosis. Although it has proved difficult to recreate repression in laboratory circumstances a number of attempts have been made.
Levinger and Clark (1961) asked participants to generate associated words with words presented by them. Some of these words were emotionally neutral e.g. tree, window and others were emotionally arousing e.g. angry, quarrel. When asked to recall these associated words results showed that people tended to recall the emotionally neutral ones as opposed to the emotionally provoking ones, which helps to support the idea of repression. However such tests are considered suspect and Holmes (1990) concluded that there is no experimental support for the concept of repression.
Recently research has focused upon repressed memories associated with child sexual abuse and whether or not recovered memories are genuine. The main problem with assessing whether or not they are true is that they have no independent, objective corroborative evidence. Williams (1992) found that 38 percent of a group of African-American women who were known to have suffered abuse reported repressed memories about it although it was clear that some of these memories were false. Loftus (1997) conducted an extensive review of studies that led him to believe that even psychologically healthy individuals altered their memory of events based on false suggestions about them. Baddelley concluded that it is important to exercise great caution in interpreting such reports.
A Summary of Forgetting
