Memory

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The Multi-store model

Proposed by Atkinson and Shiffrin. They proposed that memory consisted of three stores: sensory register, short-term memory (STM) and long-term memory (LTM).

Sensory Register

+ Duration: ¼ to ½ second + Capacity: all sensory experience (v. larger capacity)

+ Encoding: sense specific (e.g. different stores for each sense)

Short Term Memory

+ Duration: 0-18 seconds + Capacity: 7 +/- 2 items

+ Encoding: mainly acoustic

Long Term Memory

+ Duration: Unlimited + Capacity: Unlimited

+ Encoding: Mainly semantic (but can be visual and acoustic)

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Research study

Glanzer and Cunitz showed that when participants are presented with a list of words, they tend to remember the first few and last few words and are more likely to forget those in the middle of the list. Words early on in the list were put into long term memory (primacy effect) because the person has time to rehearse the word, and words from the end went into short term memory (recency effect).

Other compelling evidence to support this distinction between STM and LTM is the case of KF (Shallice & Warrington, 197) who had been in a motorcycle crash where he had sustained brain damage. His LTM seemed to be unaffected but he was only able to recall the last bit of information he had heard in his STM.

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Long term memory

Procedural memory is a part of the long-term memory is responsible for knowing how to do things, i.e. memory of motor skills such as riding a bike.

Semantic memory is a part of the long-term memory responsible for storing information about the world.  This includes knowledge about the meaning of words, as well as general knowledge.

Episodic memory is a part of the long-term memory responsible for storing information about events (i.e. episodes) that we have experienced in our lives. 

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Working memory model

The working memory model (Baddeley and Hitch, 1974) replaced the idea of a unitary STM. It suggests a system involving active processing and short-term storage of information.

The central executive has a supervisory function and acts as a filter, determining which information is attended to. It can process information in all sensory forms, directs information to other slave systems and collects responses. It has limited a limited capacity and deals with only one piece of information at a time.

One of the slave systems is the phonological loop which is temporary storage system for holding auditory information in a speech based form. It has two parts: (1) the phonological store (inner ear), which stores words you hear; and (2) the articulatory process (inner voice), which allows maintenance rehearsal.

The second slave system is the Visuospatial sketchpad (VSS). The VSS is a temporary memory system for holding visual and spatial information. It has two parts: (1) the visual cache (which store visual data about form and colour), and (2) the inner scribe (which records the arrangement of objects in the visual field.

The third slave system is the episodic buffer which acts as a backup.

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Research study for WM

Baddeley and Hitch conducted an experiment in which participants were asked to perform two tasks at the same time (dual task technique). A digit span task which required them to repeat a list of numbers, and a verbal reasoning task which required them to answer true or false to various questions (e.g. B is followed by A?).

Results: As the number of digits increased in the digit span tasks, participants took longer to answer the reasoning questions, but not much longer - only fractions of a second. And, they didn't make any more errors in the verbal reasoning tasks as the number of digits increased.

Conclusion: The verbal reasoning task made use of the central executive and the digit span task made use of the phonological loop.

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Explanations for forgetting - Interference

Interference is an explanation for forgetting from long term memory – two sets of information become confused.

  1. Proactive interference (pro=forward) is where old learning prevents recall of more recent information. When what we already know interferes with what we are currently learning – where old memories disrupt new memories.

  2. Retroactive interference (retro=backward) is where new learning prevents recall of previously learned information. In other words, later learning interferes with earlier learning - where new memories disrupt old memories.

Postman (1960) provides evidence to support the interference theory of forgetting. A lab experiment was used, and participants were split into two groups. Both groups had to remember a list of paired words – e.g. cat - tree, book - tractor. The experimental group also had to learn another list of words where the second paired word if different – e.g. cat – glass, book – revolver. The control group were not given the second list.

All participants were asked to recall the words on the first list. The recall of the control group was more accurate than that of the experimental group. This suggests that learning items in the second list interfered with participants’ ability to recall the list. This is an example of retroactive interference.

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Explanations of forgetting - Retrieval failure

Retrieval failure is where information is available in long term memory but cannot be recalled because of the absence of appropriate cues.

Context - external cues in the environment, e.g. smell, place etc. Evidence indicates that retrieval is more likely when the context at encoding matches the context at retrieval.

State - bodily cues inside of us, e.g. physical, emotional, mood, drunk etc. The basic idea behind state-dependent retrieval is that memory will be best when a person's physical or psychological state is similar at encoding and retrieval.

Organisation - Recall is improved if the organisation gives a structure which provides triggers, eg categories.

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Research study for retrieval failure

Baddeley (1975) asked deep-sea divers to memorize a list of words. One group did this on the beach and the other group underwater. When they were asked to remember the words half of the beach learners remained on the beach, the rest had to recall underwater.

Half of the underwater group remained there and the others had to recall on the beach. The results show that those who had recalled in the same environment (i.e. context) which that had learned recalled 40% more words than those recalling in a different environment. This suggests that the retrieval of information is improved if it occurs in the context in which it was learned.

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Eyewitness testimony - Misleading information

Forty-five American students formed an opportunity sample. This was a laboratory experiment with five conditions, only one of which was experienced by each participant (an independent measures experimental design).

Participants were shown slides of a car accident involving a number of cars and asked to describe what had happened as if they were eyewitnesses. They were then asked specific questions, including the question “About how fast were the cars going when they (hit/smashed/collided/bumped/contacted ) each other?”

The estimated speed was affected by the verb used. The verb implied information about the speed, which systematically affected the participants’ memory of the accident.

Participants who were asked the “smashed” question thought the cars were going faster than those who were asked the “hit” question. The participants in the “smashed” condition reported the highest speeds, followed by “collided”, “bumped”, “hit”, and “contacted” in descending order.

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Eyewitness testimony - Anxiety

When we are in a state of anxiety, we tend to focus on whatever is making us feel anxious or fearful, and we exclude other information about the situation. If a weapon is used to threaten a victim, their attention is likely to focus on it. Consequently, their recall of other information is likely to be poor.

A study by Yuille and Cutshall (1986) contradicts the importance of stress in influencing eyewitness memory. 21 witnesses observed a shooting incident in Canada outside a gun shop in which 1 person was killed and a 2nd seriously wounded. The incident took place on a major thoroughfare in mid-afternoon.

All of the witnesses were interviewed by the investigating police, and 13 witnesses (aged 15-32 yrs) agreed to a research interview 4-5 months after the event. The witnesses were also aksed to rate how stressed they had felt at the time of the incident, using a 7 point scale. The eyewitness accounts provided in both the police and research interviews were analysed and compared.

The results of the study showed the witnesses were highly accurate in their accounts, and there was little change in amount or accuracy of recall after 5 months. The study also showed that stress levels did not have an effect on memory, contrary to lab findings. All participants showed high levels of accuracy, indicating that stress had little effect on accuracy.

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Cognitive Interview

Context Reinstatement Trying to mentally recreate an image of the situation, including details of the environment, such as the weather conditions, and the individual’s emotional state including their feelings at the time of the incident. Recall from a Changed Perspective Trying to mentally recreate the situation from different points of view e.g. describing what another witness present at the scene would have seen. Recall in Reverse Order The witness is asked to describe the scene in a different chronological order e.g. from the end to the beginning. Report Everything The interviewer encourages the witness to report all details about the event, even though these details may seem unimportant.

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