Memory and Forgetting

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Coding, Capacity and Duration of Memory

Coding: The format which information is stored in the various memory stores.

Capacity: The amount of information that can be held in a memory store.

Duration: The Length of time information can be held in memory.

Short Term Memory (STM): The limited capacity memory store. Coding is mainly acoustic and the capacity is between 5 and 9 items on average, duration is between about 18 and 30 seconds.

Long Term Memory (LTM): The permanent memory store. Coding is mainly semantic, it has unlimited capacity and can store memories for up to a lifetime.

Research on Coding

Alan Baddeley - Gave different lists of words to four groups of participants to remember: Group 1 - Acoustically similar (words that sound similar), Group 2 - Acoustically dissimilar ( words that sound different) , Group 3 - semantically similar (words with similar meanings, Group 4 - semantically dissimilar.

Participants were shown the original words and asked to recall them in the correct order. When they had to do this immediately after (STM) they tended to do worse with acoustically similar words. If they were asked to recall the word list after a time interval of 20 minutes (LTM) they did worse on semantically similar words.

Multi - Store Model of memory

Sensory Register

Stimulus from the environment will pass through the sensory register. Then enters the sensory stores: Iconic (info is coded visually) and Echoic (info is coded acoustically). Material in the sensory registers lasts only briefly before it goes to the Short Term Memory. If it is then rehearsed it passes to the Long Term Memory where it can be retrieved back into STM where the memory can then be recalled.

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Types of Long- Term Memory

Episodic Memory

A store for personal events. It includes memories of when the event occurred and of the people, objects, places and behaviours involved. Memories from this store have to be retrieved consciously and with effort.

Semantic Memory

A store for our knowledge of the world. It includes facts and our knowledge of what words and concepts mean. These memories usually need to be recalled deliberately.

Procedural Memory

A store for our knowledge of how to do things. This includes our memories of learned skills. We can usually recall these memories without making a conscious or deliberate effort.

The Working Memory Model

An explanation as to how STM is organised and how it functions.

Central Executive - The component that co-ordinates the activities of the three slave systems and allocates processing resources to those activities.

Phonological Loop - The component that processes information in terms of sound. This includes both written and spoken material. It is divided into the phonological store and the articulatory process.

Visuo-spatial Sketchpad - The component that processes visual and spatial information in a mental space often called our 'inner eye'.

Episodic Buffer - The component that brings together material from the other subsystems into a single memory rather than separate strands. It also provides a bridge between working memory and long-term memory.

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Explanations for Forgetting

Interference

At least some forgetting takes place because of interference. This occurs when two pieces of information conflict with each other, resulting in forgetting of one or both of the memories.

Proactive Interference - This is when an older memories, that have already been stored, disrupt the recall of newer memories.

Retroactive Interference - This is when newer memories disrupt the recall of older memories already stored. The degree of forgetting is again greater when the memories are similar.

Retrieval Failure

The reason people forget information could be due to insufficient cues. When information is initially placed in memory, associated cues are stored at the the same time .

If these cues are not available at the time of recall, it may make it appear as if you have forgotten the information.

Encoding Specificity Principle (ESP) - Endel Tulving reviewed research into retrieval failure and concluded that if a cue is to help us recall information then it must be present at encoding and at retrieval.

Context Dependant Forgetting (External Cues) - Godden and Baddeley carried out research into context dependant forgetting. They studied deep sea divers in which they learnt a list of words both on land and underwater and then had to recite them either on land or underwater. They found that accurate recall was 40% lower in the non-matching conditions. The external cues at learning were different to those at recall hence retrieval failure.

State Dependant Forgetting (Internal Cues) - Carter and Cassaday (1998) gave anit- histamines drugs to their participants. They made the Ps go slightly drowsy. This created an internal physiological state different from the 'normal state' of being awake and alert. They had to learn a list of words. In the conditions where there was a mismatch between internal state at learning and recall, performance on the memory test was significantly worse.

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Factors affecting Eyewitness testimony

Misleading Information

Leading Questions

A question which because of the way it is phrased, suggests a certain answer. For example, 'Was the knife in the accused's left hand?'. This suggests the answer if 'left hand'.

Loftus and Palmer (1974) - They showed a film clip of a car accident to participants and gave them questions after about the accident. In the critical question (a leading question) participants were asked to describe how fast the 'car was going when they hit each other?'. This is a leading question because the verb 'hit' suggests the speed of the car was going. There were 5 groups and each group was given a different verb in the critical question. The different words were 'hit', 'contacted', 'bumped', 'collided' and smashed. The verb 'contacted' got a mean estimate speed of 31.8mph and the verb 'smashed' got a mean estimate of 40.5mph. This proves that a leading question can affect a witness' recall of an event.

Post- Event Discussion

When co-witnesses to a crime discuss it with each other their eyewitness testimonies may become contaminated. This is because they combine (mis)information from other witnesses with their own memories.

Fiona Gabbert et al. studied participants in pairs. Each participant would watch a video of the same crime, but filmed from different points of view. This meant that each participant could see elements in the event that the other could not. Both participants then discussed what they had seen before individually completing a test of recall.

The researchers found that 71% of the participants mistakenly recalled aspects of the event that they did not see in the video but had picked up in the discussion. The figure in the control group, who didn't discuss with the others, had a figure of 0%.

Anxiety

Anxiety has a negative effect on recall

Anxiety creates physiological arousal in the body which prevents us paying attention to important cues.

Johnson and Scott (1976) did research into the effect weapons (to create anxiety) had on recall. They led participants to believe they were going to take part in a lab study. While in the waiting room the participants would hear an argument in the next room. In the 'low anxiety' condition a man walked through the waiting area, carrying a pen with grease on his hands. In the 'high anxiety' conditions participants heard the same argument but then a man walked through the waiting area holding a paper knife covered in blood.

The participants later picked out the man from a set of 50 photos; 49% of the participants who saw the man carrying the pen were able to identify him. The corresponding figure for the participants who had seen the man with the paper knife was 33%. The tunnel theory of memory argues that a witness's attention narrows to focus on a weapon, because it is a source of anxiety.

Anxiety had a positive effect on recall

The stress of witnessing a crime or accident creates anxiety through physiological arousal within the body. The flight or fight response is triggered which increased our alertness and improves our memory for the event because we become more aware of cues in the situation.

John Yuille and Judith Cutshall (1986) conducted a study of a real-life shooting in a gun shop in Vancouver, Canada. The shop owner shot a thief shot dead. There were 21 witnesses - 13 agreed to take part in the study. The interviews were held 4-5 months after the incident and these were compared with the original police interviews made at the time of the shooting. Accuracy was determined by the number of details reported in each account. The witnesses were also asked to rate how stressed they had any emotional problems since the event, such as sleeplessness.

The witnesses were very accurate in their accounts and there was little change in the amount or accuracy after 5 months - though some details were less accurate., such as recollection of the color of items and age/height/weight estimates. Those participants who reported the highest level of stress were most accurate in recall.

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