Memory : Models, Forgetting, Flashbulb Memories

Memory : Models, Forgetting, Flashbulb Memories (06-Feb-2003)

Multi-Store Model

Atkinson & Shiffrin (1971) proposed the two-process model of memory, which has information being transferred from STM to LTM by a process of rehearsal. This model has a number of strengths:

case studies (e.g. Milner's study of "HM") appear to support it
many studies (Miller, Peterson & Peterson, etc.) support this model
this model stimulated a great deal of research into the way that memory worked

On the other hand:

case studies (e.g. Shallice & Warrington's study of "KF", who was apparently able to form new LTMs without being able to form new STMs), suggest that information can get into LTM without going through STM
Miller's idea of "chunking" appears to show that the information flow from STM to LTM is not just one way: for the STM to arrange information into "chunks", it presumably has to draw on information in LTM
much of the research into STM/LTM has been carried out in experimental settings where P's are asked to remember meaningless series of data. This is not representative of how people normally remember things
rehearsal (i.e. repeating information over and over) appears to be a very bad way to learn information; e.g. Bekerian & Baddeley (1980) reported that few people remembered information about BBC radio frequency changes despite having heard hundreds of advertisements

Levels of Processing (LOP)

Craik & Lockhart (1972) suggested that how well we remember things is determined by how much processing is applied to the information. They define three processing levels:

superficial, or shallow
intermediate, or phonetic
deep, or semantic

Craik and Lockhart showed P's a list of words and asked questions about them. One set of P's ("superficial") were asked questions such as "is it written in capital letters?", the next set ("intermediate") were asked "does it rhyme with ...?", and the third set ("deep") were asked "would it fit into a sentence such as ...?". The P's were later asked to recall as many words from the list as they could, with the following results:

superficial : 15%
intermediate : 35%
deep : 70%

Craik & Lockhart conclude that maintenance rehearsal (simply repeating something over and over again) is not an effective way to remember; what is more effective is elaborative rehearsal, i.e. applying some meaning to the information. Compared with the multi-store model, in which the amount of rehearsal is the important factor, the LOP model says that is the kind of rehearsal that is important.

Craik & Tulving (1975) performed an experiment which supported LOP; they flashed a series of words to P's and asked them questions which would require a different level of processing. Subsequently when asked to recall the words, P's did significantly better for words for which "deep" processing had been required.

According to LOP theory, memory is little more than a by-product of the way that information is processed.

The LOP model is criticised because:

It's difficult to define what "deep" means, and to measure how "deep" a level of processing is occurring
It offers an explanation for what is happening, but doesn't explain why "deep" processing results in better memory
An alternative explanation of why "deep" processing works is simply that "deeper" levels of processing require more time, and therefore work simply by providing more opportunity for rehearsal

Working Memory

Baddeley & Hitch(1974) proposed this model. While accepting a distinction between STM and LTM, they argued that STM is more than just a first step before LTM, and that it is made up of a components working together, rather like a computer. The components include:

the central executive is what pays attention to whatever we're concentrating on, and delegates certain types of work to other components
the visuo-spatial scratchpad (or "inner eye") comes into play when, for example, we mentally walk through our house to count the windows.
the articulatory or phonological loop (or "inner voice") is like a sub-vocal speech, so would be used to count the windows that we "see".
the acoustic, or phonological store is independent of the articulatory loop, retaining the memory of acoustic information long enough for it to be made sense of.

Some strengths of the Working Memory model are:

PET scans on P's performing certain "STM" show that different types of tasks stimulate activity in different physical regions of the brain, suggesting that STM is more complex than the simple model put forward by Atkinson & Shiffrin
It has been shown (Baddeley 1975) that P's are more capable of performing two tasks that require distinct WM components than when asked to perform two tasks that use a common component

Weaknesses:

Little is understood about the central executive, which is the most important of all components
Much of the evidence for this model has been derived from laboratory studies; it's not clear how well these reflect the way that memory works in present "real life" situations.

Forgetting

Suggested causes of forgetting in STM are:

Peterson & Peterson (1959) suggested that trace decay involves the gradual decay of a memory trace, in which items in STM will be lost over time. However, Jenkins & Dallenbach (1924) showed that P's who sleep remember more when they wake than P's who stayed awake for the same amount of time. This suggests an alternate possibility:
Waugh & Norman (1965) showed that displacement could account for STM forgetting; as new information enters STM, existing information is displaced, and therefore forgotten.

and in LTM:

Bower (1969) showed that lack of semantic organisation material meant that it was less likely to be recalled. Two sets of P's were shown the same set of words, with one group of P's seeing the words in a random order, and the other group seeing the words arranged into a meaningful heirarchy. The second group of P's scored around three times better on subsequent recall tests
Craik & Tulving's experiment showed that lack of elaboration meant that less information would be recalled
Tulving & Pearlstone (1966) showed that forgetting can be a retrieval failure caused by a lack of a cue. Cues can be of different types:
- context-dependent ("external") cues are provided by environmental factors. Abernathy (1940) showed that P's performed better when they were were asked to recall information while in the same room as where they'd learned it compared to P's who were asked to recall information while in a different room
- state-dependent ("internal") cues are provided the internal state of a P. Goodwin et al (1969) showed that alcoholics who were unable to remember find money that they'd hidden whilst drunk, but could find it when they became drunk again. McCormick & Mayer (1991) showed that we are more likely to remember happy events when we feel happy.

Interference theory suggests that forgetting is caused by new and old memories interfering with one another. In retroactive interference, a new memory interferes with an old one; for example having learned German and then French, you might come up with a French word when trying to remember a German one. Proactive interference occurs when an old memory interferes with a new one. Keppel & Underwood (1962) suggested that interference may have been a factor in Peterson & Peterson's experiment.

As we saw last week, forgetting can be caused by a physical problem such as brain damage or disease.

Another possible cause of forgetting is repression as described by Freud. In this case, a memory that is too uncomfortable is kept in the unconscious. Bradley and Baddeley (1990) attempted to prove this experimentally by testing P's recall of emotionally arousing words. They found that while an immediate test indicated repression (P's recalled fewer of the emotionally charged words), a test carried out 4 weeks later had the same P's recalling more of the emotionally charged words. Eysenck & Wilson (1973) suggest that the emotional arousal felt by the P's when they first hear the words is significant, causing them to forget (rather than repress) the words on the first test, but helping them to recall the words in the later test.

Flashbulb Memories

Brown & Kulik (1977) (see study sheet) described flashbulb memories, suggesting that dramatic events can imprint a powerful impression in peoples' memories, and argued that there may be some physiological process involved in encoding such a memory. Such events as the Kennedy assassination, or Princess Diana's death are examples that trigger flashbulb memories. Neisser (1976) suggested that in fact FM are a result of rehearsal - dramatic events are likely to be ones that we think of over and over again.

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