Psychology                                                                                                              

Psychology Revision – Memory

Definitions within Memory

Memory

  • The mental process used to encode, store and retrieve information.  

Encoding

  • Encoding involves changing the information presented into a different form. Since words or other items in the short term store are rehearsed or repeated, we might assume that they are encoded in terms of their sound (acoustic coding). In contrast, the information we have stored in the long term memory nearly always seems to be stored in terms of its meaning (semantic coding).
  • Encoding takes many different forms; visual, auditory, semantic, taste and smell.

Capacity

  • The short term store has very limited capacity, about 7 items. In contrast the capacity of the long term memory is assumed to be so large that it cannot be filled, it is said to have unlimited capacity and lasts potentially forever.

Duration

  • Information lasts longer in the long term store than in the short term store,. There is evidence that in the short term store, if not rehearsed, information will disappear within about 18 – 20 seconds and in contrast there is evidence that elderly people can recognise the names of fellow students from 48 years previously.

Storage

  • As a result of encoding, the information is stored in the memory system; it can remain stored for a very long time maybe a entire lifetime.

Retrieval

  • Recovering information from the memory system. Can be known as recall or remembering.

Short term Memory

Definition

  • Short term Memory – A temporary place for storing information. Short term memory has a very limited capacity and short duration, unless the information within it is maintained through rehearsal.

Capacity in STM (Jacobs):

AIMS:

  • To investigate how much information can be held in short term memory.
  • To do this, Jacob’s needed an accurate measure of STM capacity – he devised a technique called the serial digit span
  • His research was  the first systematic study of STM

PROCEDURES:

  • This was a laboratory study using the digit span technique
  • P’s were presented with a sequence of letters or digits
  • This was followed by a serial recall (repeating back the letters or digits in the same order they were presented)
  • The pace of the item presentation was controlled to half second intervals through a metronome
  • Initially, the sequence was 3 items – it was then increased by a single item until the participant consistently failed to reproduce the sequence correctly
  • This was repeated over a number of trials to establish the participants’ digit span.
  • The longest sequence length that was recalled correctly on at least 50% of the trials was taken to be the P’s STM digit span

FINDINGS:

  • Jacobs found that the average STM span (number of items recalled) was between 5 and 9 items
  • Digits were recalled better (9.3 items) than letter (7.3 items)
  • Individual differences were found, explaining the range of 5-9
  • STM span increased with age – in one sample he found an 6.6 average for 8 year old children compared to 8.6 for 19 year olds

CONCLUSIONS:

  • The findings show that STM has a limited storage capacity of between 5 and 9 items
  • The capacity of STM is not determined much by the nature of the information to be learned but by the size of the STM span, which is fairly constant across individuals of a given age
  • Individual differences of STM span increasing with age may be due to increasing brain capacity or improved memory techniques, such as chunking

EVALUATION:

  • + The study has great historical importance because it represents the first systematic attempt to assess the capacity of STM
  • - The research lacks mundane realism as the digit-span task is not representative of everyday memory demands – the artificiality of the task may have made the results biased. Letters and numbers are not very meaningful, so may not be remembered as well as meaningful information.
  • - This means that the capacity of STM may be greater for everyday memory.
  • - Jacobs’ findings cannot be generalised to real life memory – so it may have low ecological validity
  • - However, it could be argued that using more meaningful information would produce a less pure measure of STM capacity, because participants could make use of LTM to improve performance
  • + The findings have been usefully applied to improve memory (phone numbers etc). Memory improvement techniques are based on the findings that digit span cannot be increased, but the size of the bits of information can be – this is what happens in chunking.

Encoding in STM (Conrad)

AIMS:

  • To test the hypothesis that short term memory encodes information acoustically

PROCEDURES:

  • Conrad (1964) compared performance with acoustically and visually presented data.
  • Presented p’s with 6 letters at a time, for 0.75 seconds
  • P’s had to recall the letters in the order they were shown

FINDINGS:

  • Letters were presented visually, but ones which sounded the same were confused (e.g. S was recalled instead of X)

EVALUATION:

  • - Later research showed that visual codes do exist in STM – sometimes
  • - During a different experiment (Posner’s), reaction time was longer for Aa than AA – suggesting a visual processing rather than acoustic

Key Study: PETERSON AND PETERSON – DURATION IN SHORT TERM MEMORY.

Aims:

  • They aimed to study how long information remains in short term memory, using simple stimuli and not allowing the participants to rehearse the material presented to them
  • They wanted to test the hypothesis that information not rehearsed is lost rapidly from short-term memory.

Procedures:  

  • They used the ‘Brown-Peterson’ technique.
  • On each trial participants were presented with a trigram consisting of 3 consonants e.g. BVM, CTG which they knew they would have to recall in the correct order.
  • Recall was required after a delay of 3, 6, 6, 12, 15, or 18 seconds.
  • Between the initial presentation of the trigram and the time participants were asked to recall, they were told to count back in threes from a random 3 digit number e.g. 866, 863, 860… this was done to prevent rehearsal.
  • Participants were tested repeatedly with the various time delays and the effect of the time delay on memory was assessed in terms of the number of trigrams recalled.

Findings:

  • There was a rapid increase in forgetting from the STM s the time delay increased.
  • After 3 seconds 80% of the trigrams were recalled.
  • After 6 seconds 50% were recalled
  • After 18 seconds fewer than 10% of the trigrams were recalled.
  • Therefore very little information remained in the STM for more than 18 seconds.

Conclusions:

  • The findings suggest strongly that information held in the STM is rapidly lost when there is little or no opportunity for rehearsal.
  • Thus information in the STM is fragile and easily forgotten

Evaluation:

  • - They used artificial stimuli (i.e. trigrams), which have very little meaning and therefore the experiment lacks mundane realism and external validity.
  • - The participants were given many trails with different trigrams so may have become confused.
  • - Peterson and Peterson only considered STM duration for one type of stimulus, and did not provide information about duration of STM in other kinds of stimuli e.g. pictures, smells, melodies.
  • + It was a well controlled lab experiment, which allows a cause and effect relationship to be established.
  • + Repeated measures design
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Long term Memory

Definition

  • Long term Memory – A relatively permanent store, which has unlimited capacity and duration. Different kinds of long term memory have been identified; episodic (memory for personal events), semantic (memory for facts and information) and procedural (memory for actions and skills).

Key Study: BAHRICK ET AL – DURATION IN LONG TERM MEMORY.

Aims:

  • Bahrick et al aimed to investigate the duration of very long term memory (VLTM), to see if they could last over several decades and thus support the assumption that the duration of long term memory can last a life ...

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