- Information from STM leaves a trace in the brain (engram) caused by excitation of neurons
- A trace DECAYS unless it is rehearsed
- A permanent engram is formed once learned – transfers to LTM
Waugh and Norman (1965)
Aim: investigating forgetting in a short-term memory task. Method: participants had a list of 16 digits. In one condition, the list was presented at the rate of one per second. In the other, it was presented at a rate of four per second. After presentation of the list, participants were given a cue to indicate which of the sequence of 16 digits they had to recall. They suspected that if the decay theory alone is responsible for forgetting, there would be more forgetting in the first condition because it took longer to read out so more time had passed.
Result: No significant different in recall was found between 2 conditions
Conclusion: These findings do not support the decay theory, as they suggest that the passage of time alone cannot explain forgetting in this short-term memory task.
Evaluation of Decay
- Most studies of decay involve unrealistic tasks so have very low ecological validity
- Decay theory is difficult to investigate in a real-life way because the time learning something and recalling it will be filled with all kinds of different events. In studies that involve the distracter task, it might be this that is responsible for forgetting and not simply the passage of tijme. This supports intereference theory rather than decay theory
- Decay theory cannot describe why people often remember things that happened a long time ago, even though they have not thought about them for ages.
- There is no evidence that neurological decay is responsible for forgetting, although it is obviously responsible for forgetting in conditions such as Alzheimer’s disease.
Proactive Interference – things we have previously learned interferes with what we have learned more recently. Interference works forward in time (hence proactive) E.g. calling your new partner by your previous partner's name!
Retroactive interference – things we have learned more recently intereferes with what we have previously learned. Interference works backwards (retroactive) E.g. forgetting how to use your old mobile when you have become used to the new model.
Interference has been found to be far greater when the two sets of information are very similar, for example when trying to learn two different foreign languages.
Baddeley and Hitch (1977)
Aim: wanted to compare interference and decay explanations for forgetting
Method: rugby players were asked to recall the names of the teams they had played earlier in the season. Thtough the season, different players played different numbers of games because some had missed games through injury or for another reason. B and H looked at how recall was affected by both number of intervening games (interference) and the amount of time that had passed since each game was played. (decay)
Results: showed that forgetting was affected by the number of intervening games a player had played, rather than by the time that had passed since the game
Conclusion: Supports the interference theory rather than the decay theory
Evaluation of Interference
- Although the effects of interference have been demonstrated in experiments, there is no real explanation of why these affects occur or of the cognitive processes occur
- Most research into the effects of interference on forgetting involves artificial stimuli – usually lists of unrelated words – and the studies have taken place in a lab. This might suggest that interference in real life may be more complex and varied
- Some researchers have investigated ‘real-life’ events and have provided evidence for this theory
- It is clear that interference does have some role in forgetting, but the extent of the effect is uncertain.
- We forget because we cannot retrieve information from long-term memory wthout the appropriate retrieval cues. In this case, the information is available, because it is still stored in memory, but not accessible, because we cannot recall it when needed.
- Tip-of-the-tounge phenomenon (TOT) Brown and McNeill (1966)
- Cues are used to remember, one useful cue is context. – Memory is context-dependent meaning that recall is dependent on whether the context in which we learn is the same as the context in which we recall.
- Other cues – category headings
Godden and Baddeley (1975)
Aim: investigated the importance of environmental context in memory and forgetting
Method: participants were divers who had a list of 40 unrelated words either on the beach or underwater. After hearing the words, the participants were tested for recall either in the same environmental context or different.
Results:Rparticipants recalled more words if they were tested in the same environment as where they learned the words.
Conclusion: study demonstrates that recall performance is best when the environmental context is the same. Supports retrieval failure because it shows how being in a different context than at the time of learning and the time of recall causes us to forget some of the information.
Evaluation of Retrieval Failure
- According to Baddeley, there is no doubt in the importance of cues in the retrieval process
- Godden and Baddeleys finsdings in the underwater study occur only when participants are asked to perform free recall, and not when the test involves recognition. So retrieval failure may not explain the insances of forgetting that occur with other forms of recall
- The context-dependent nature of memory has been demonstrated many times and it is not even necessary to be in the same environment i.e. you can just imagine the environment
- Some studies involve artificial stimuli so lack ecological validity
- The retrieval failure explanation of forgetting is consistent with the levels of processing theory of memory. Deep processing involves making links and associations with what we already know. This increases the chance that one of more of these associations will match with a retrieval cue.
Based on Atkinson and Shriffin’s MSM, stated that short-term memory has a limited capacity of seven, plus or minus 2 items.
The limited capacity of the short-term memory meant that any extra information would push out or displace information already in the short-term memory.
Example : imagine a shelf
Displacement can also explain the recency effect in serial position effect studies. If displacement theory is correct, it is possible to disrupt the recency effect by giving participants another task, such as reciting a nursery rhyme. This would displace the worlds helf in the short-term store and the recency effect would disappear
Evaluation of Displacement
- The theory is consistent with Atkinson and Shriffin’s model of short-term memory.
- As Atkinson’s description of short-term memory gave way to the working memory model, displacement became less popular
- Displacement is a fairly limited explanation for forgetting as it can only explain forgetting from short-term memory
- In studies involving an interference task, forgetting may be due to decay because of the extra time between learning and recall, rather than being due to displacement.
Lack of Consolidation
This explanation has a biological basis.
Describes the making of memories as ‘permanent alteration of the brain substrate in order to represent some aspect of past experience’. The permanent change that takes place in brain cells when memories become fixed is called consolidation.
Refers to brain cells or neurons and how they are connected via synapses. At the synapse, chemicals known as neurotransmitters are passed from one neuron to another. In any network of connecting neurons there will be a pattern of stimulation and inhibition. Brain research suggests that the pattern of activity between connecting neurons forms the basis for making a memory.
Yarnell and Lynch (1970)
Aim: to investigate the effects of head trauma and concussion on memory loss
Method: field study of American footballers who had been concussed during the game. As soon as they came round, they were asked about the details of play at the time of the incident and then asked again between 3 and 20 minutes later
Results: When asked immediately, the footballers gave accurate information. However, when asked later after regaining consciousness, they could give no information
Conslusions: The blows to the head received by the players let to a disruption of the consolidation process needed to make a memory trace permanent. Failure to recall events from concussion cannot be due to a failure to take in the info in the first place, as it was available for recall immediately after regaining consciousness. This supports the lack of consolidation theory
Evaluation of Lack of Consolidation
- The explanation is consistent with what we know about the nervious system and how the brain processes information
- The theory links both biological and psychological approaches to explaining human behaviour
- There is still no clear evidence about exactly how long is required for consolidation to take place
- Most instances of forgetting in real life do not involve interference with psychoactive drugs, a blow to the head or brain surgery. Maybe lack of consolidation only occurs rarely in real life.
Motivated Forgetting - Repression
Repression is sometimes referred to as motivated forgetting, meaning that we forget things because we wish to forget them.
Psychodynamic theory – we have a set of unconscious defence mechanisms to protect our conscious self from unpleasant thoughts or events.
Repression is a defence mechanism whereby unpleasant memories are pushed out into the unconscious, so that the conscious self is not upset by them.
Our conscious behaviour may be affected by the memories prescence. For example someone who has repressed a childhood horrific accident may suffer from unexplained anxiety disorders as an adult.
Aim: set out to see whether women recalled incidents of childhood abuse
Method: participants were 129 women, shown by documentation to have been abused between the ages of 10 months and 12 years. When interviewed they were between 18-31 years ols.
Results: in extended interviews about their sexual histories, 30% of women failed to report the abusive episode documented by the hospital. They did quite often report their general experience of having been abused
Conclusion: some participants failed to recall specific incidents of abuse because these had been repressed
Evaluation of Motivated Forgetting - Repression
- The general problem is that it cannot be tested easily, defence mechanisms are unconscious processes, so cannot be investigated.
- Word-association studies are not very realistic, because memory for real-life unpleasant events is much more emotionally disturbing than a list of unpleasant words
- In Williams’s study, there may have been other explanations for the failure to recall abuse. They might not wish to talk about it, they might be embarrassed, might want to protect parents.
- Findings in single cases of dissociative amnesia should not be generalised to explain other cases of forgetting
- Our own experience tells us that many people do recall unpleasant memories so why would we repress some but not others?
- There is evidence that people who have suffered upsetting experiences are more likely to be affected by anxiety disorders, although this finding does not directly support the theory of repression.