Models of memory

The Multi-store model

•Most well-known early model of memory processes•Necessary first step•Dominant model in no-scientific ideas about memory•Central part of study of this process

• Atkinson and Shiffrin 1968• Developed model to explain how memory is

organized• Consists of 3 basic stores– Sensory– Short term– Long term

Information must pass through all stages to get to the end

• information received is sensory (visual, auditary, smell, touch).

• Held in sensory stores for initial processing before passing it on to STM (will decay if we don’t get to it)

• Info is either iconic or echoic • Duration .5 (visual) – 4 seconds (echoic)

– Iconic storage = visual information– echoic storage = auditory or sound information.

• Information from sensory memory is passed to short term memory by attention i.e. taking notice of something.

Sensory Store

Sperling (1960)Aim - To investigate the capacity of iconic memory.Method - A three by four grid of numbers was flashed for 0.05

seconds. Followed by a high, medium or low pitched tone to indicate which row was to be recalled.

Results - On average, the participants were able to recall 80% of the letters on the cued row.

Conclusions - Since the participants didn't know which row was going to be called beforehand but still managed to recall it well, you can assume that at one time all of the information was held in the sensory memory. But it decayed very rapidly.

Evaluation - Sensory memory stores are large but decay very rapidly - lasting 250 to 500 milliseconds.

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Short Term Memory

Role:

• Holds on to info long enough to use itDeals with :– Incoming from sensory– Retrieval of old info from LTM (part of schemata)

• Plays important role in conscious thought• The cognitive work-space – manipulate ideas,

solve problems

Characteristics of STM

• Duration – 15 – 30 seconds (Atkinson et. al.); 6 – 12 (Crane)– Extend through rehearsal, repetition (inner speech)

• Capacity– 7 items +/- 2 (Miller 1956)– Can increase capacity through ‘chunking’ –

grouping information– STM = ‘leaky bucket’– The more items you put in, the more you displace

Coding• Primarily acoustic• Conrad (1964) – letters that sound similar

more likely to be confused than those that sound different

• Can also be coded semantically

Long Term Memory (LTM)

• More permanent• Use past experiences and knowledge for

future• Bower (1975) – examples = spatial maps,

social norms• Indefinite duration• Unknown capacity• Coding is primarily semantic and visual

Evaluation

Do separate stores exist?

• To justify the existence of three qualitatively different types of memory store (sensory, short-, and long-term), we must show major differences between them.– Temporal duration– Storage capacity– Forgetting mechanism(s)– Effects of brain damage.

RECAP

• Activated information from long-term memory is in short-term memory,

• Decay of that activation causes that information to leave short-term memory, and

• Decay can be prevented by rehearsal.

Evidence supports separate sensory, short-term, and long-term stores

BUT process oversimplified

Reality is more complex than unitary short-term and long-term stores– Warrington and Shallice (1972) showed that short-

term memory is not unitary. (based on a single store)– Shallice and Warrington (1974) showed that a

patient (KF) had variable problems with short-term memory of different types of information.

– Logie (1999) discussed that short-term memory often involves accessing the long-term store.

AND THE THEORY IGNORES:

• roles of proactive interference • Roles of retrieval cues in short-term memory

and forgetting

EVIDENCE• The theory states that forgetting is due to decay, however

proactive interference also has a role (Keppel & Underwood, 1962).

• If forgetting is due to decay, forgetting should be rapid in the absence of rehearsal.– This was observed by Peterson and Peterson (1959) but

contradicted by Nairne et al. (1999; see E&K p. 194).

• Tehan and Humphreys (1996) present evidence against the assumption that information in short-term memory is directly accessible and depends on the nature of the retrieval cue (see E&K p. 194).

THUS

Overall Evaluation

• Most assumptions in the standard model are either incorrect or only partially correct.

Working Memory Model

• A model of STM

• Does not see the STM store as unitary• BUT consisting of several components

(see notes)

http://generallythinking.com/blog/6-strengths-of-the-working-memory-model/

Exploration and activities

• http://www.psypress.co.uk/ek5/resources/demo_ch06-sc-02.asp

Strengths

• explains not only the storage, but also the processing of information.

• Because the model proposes specific and separate functions and subsystems, new predictions and hypotheses can be drawn up for testing (specificity)

• Consistent - with records of brain-damaged patients. – Eg. the visuo-spatial sketch pad is said to be made of two parts

• visual cache which stores information about colour and form• inner scribe, which processes spatial and movement information.

– Patient ‘LH’ had more difficulty with visual tasks than spatial tasks, which probably means that there is a different part of the brain controlling these things; just as the model suggests

– Another example is ‘KF’, whose forgetting of auditory stimuli was higher than visual stimuli.

• Model integrates other research findings– experimental evidence which supports the model

• Baddeley and his colleagues’ word-length effect supporting the phonological loop

• a number of brain-scan studies have found different brain regions to activate when people carry out tasks involving the different components of working memory

Weaknesses

I: Components may as yet be too simple• Model does not explain the full range of day-

to-day phenomena– Eg. some things we’re pretty good at

remembering, unless someone starts talking to us while were trying to remember it.

– Is there any information that is NOT as prone to decay as it is to interference from competing input?

II: Central executive is poorly understood. • There are only modest correlations between people on

different executive functions• some people can lose some executive functions but keep

others– SO - highly unlikely that the CE is one unitary construct.

• Do not know how CE is broken down so:– difficult to come up with hypotheses to test the model further– Difficult to know how these subsections relate to each other

and the other parts of the model. – Eg. Does the CE initiate verbal rehearsal, monitor it,

maintain it? Or is it purely a function of the phonological loop?

III: Episodic buffer and how it works

• Researchers do not understand fully how the episodic buffer combines information from the other parts of the model, and from long-term memory.