Topic 1 Short Term Memory Flashcards
What does the STM do and how is it different from the LTM?
STM temporarily stores information received from the SR. It is an active (changing) memory system, as it contains information currently being thought about. STM differs from LTM especially in terms of coding, capacity and duration and how information is forgotten (see Explanations for forgetting, page 76). There are several explanations for forgetting from STM.
What is the coding in the STM?
Information arrives from the SR in its original raw form, such as in sound or vision, and is then encoded (entered into STM) in a form STM can more easily deal with. For example, if the input into the SR was the word ‘platypus’, this could be coded into STM in several ways:
- Visually - by thinking of the image of a platypus
2 .Acoustically - by repeatedly saying ‘platypus’
- Semantically (through meaning) by using a knowledge of platypuses, such as their being venomous egg-laying aquatic marsupials that hunt prey through electrolocation.
Research suggests that the main form of coding in STM is acoustic (by sound), but other codes exist too.
What research supports the coding?
What is the aim? Method?
Baddeley (1966)
Aim= To assess whether coding in STM and LTM is mainly acoustic (by sound) or semantic (by meaning).
Method=
- 75 participants were presented with one of four word lists repeated four times.
List A - acoustically similar words
List B - acoustically dissimilar words
List C-semantically similar words
List D - semantically dissimilar words
- To test coding in STM, participants were given a list containing the original words in the wrong order. Their task was to rearrange the words in the correct order.
The procedure for LTM was the same, but with a 20-minute interval before recall, during which participants performed another task to prevent rehearsal.
What were the results of Baddeley (1966) Research?
- For STM, participants given List A (acoustically similar) performed the worst, with a recall of only 10 per cent. They confused similar-sounding words, e.g. recalling ‘cap’ instead of ‘cat’. Recall for the other lists was comparatively good at between 60 and 80 per cent.
- For LTM, participants with List C (semantically similar) performed the worst, with a recall of only 55 per cent. They confused similar-meaning words, e.g. recalling ‘big’ instead of ‘huge’. Recall for the other lists was comparatively good at between 70 and 85 per cent.
What were the 2 conclusions and evaluation of the Baddeley 1966 Research? (3 advantages 1 disadvantage)
Conclusions
- For STM, since List A was recalled the least efficiently, it seems there’s acoustic confusion in STM, suggesting STM is coded on an acoustic basis.
- For LTM, since List C was recalled the least efficiently, it seems there’s semantic confusion in LTM, suggesting LTM is coded on a semantic basis.
Evaluation
Advantage
1. Baddeley’s findings make ‘cognitive sense’. For example, if you had to remember a shopping list, you’d probably repeat it aloud (acoustic rehearsal) while walking to the shops, but if you recall a book you’ve read, you remember the plot, rather than every single word.
- The small difference in recall between semantically similar (64 per cent) and semantically dissimilar (71 per cent) lists suggests there’s also semantic coding in STM.
- As a laboratory study it can be replicated to check the results so it is verifiable
Disadvantage
1. This was a laboratory study and therefore shows causality (cause and effect relationships), but may lack ecological validity (not representative of real-life activities).
What is the evaluation of the coding?
- Although research shows that coding in STM is mainly acoustic, other sensory codes, such as visual, are used too. Indeed, some stimuli like faces or the smell of food would be difficult to code acoustically. What would the sound of treacle be?
What is the capacity of the STM?
STM has a limited capacity, as only a small amount of information is held in the store. Research indicates that between five and nine items can be held, though capacity is increased by chunking, where the size of the units of information in storage is increased by giving them a collective meaning. For example, chunking the twelve letters of SOSABCITVFBI into four chunks of SOS/ABC/ITV/FBI will increase capacity.
What is chunking?
method of increasing STM capacity by grouping information into larger units
What research is there for STM capacity?
- Jacobs (1887) tested STM capacity with the serial digit span method, where participants are presented with increasingly long lists of numbers or letters and have to recall them in the right order. For example; 3, 9, 1’ (followed by recall), ‘8, 5, 3, 9’ (followed by recall), ‘2, 4, 7, 1, 3’ (followed by recall) and so on. When participants fail on 50 per cent of tasks, they are judged to have reached their capacity. Jacobs found capacity for numbers was nine items and for letters seven items, which illustrates how the capacity of STM is limited. Numbers may be easier to recall as there are only nine single-digit numbers (0-9), compared to 26 letters in the English language (A-Z).
One criticism is that experimental tasks such as recalling lists of letters have little relevance to everyday activities and so lack mundane realism.
What is the Miller (1956) and Simon (1974) research for capacity of STM?
Miller (1956) reviewed research to find the capacity of STM to be between five and nine items, but that the ‘chunk’ (pieces of information grouped together into meaningful sections) was the basic unit of STM. This means five to nine chunks can be held at any one time, increasing the store’s capacity.
Simon (1974) found that although STM capacity should be measured in terms of chunks, this varies with the type of material being recalled and the amount of information contained within the chunks.
What is the evaluation for STM capacity?
Use Daneman and Carpenter (1980) Research to support this
Other factors, like age and practice, also influence STM capacity and nowadays STM limitations are mostly seen as due to processing limitations associated with attention.
There may be individual differences in STM capacity. Daneman & Carpenter (1980) found capacity varied between five and twenty items between those with advanced and poor reading comprehension.
What is the duration of the STM?
The amount of time information remains within STM without being lost is limited to a maximum of about 30 seconds. This can be extended by rehearsal (repetition) of the information, which if done long enough will result in transfer of the information into LTM, where it will become a more long-lasting feature.
What is research for the duration of the STM?
- Peterson & Peterson (1959) read nonsense trigrams (words of three letters that don’t form recognisable words, like ZFB) to participants, and then got them to count backwards in threes from a large three-digit number (to prevent repetition of the letters) for varying periods of time. They found that around 90 per cent of trigrams were recalled correctly after three seconds, but only 5 per cent after 18 seconds, which suggests STM duration has a capacity of between 20 and 30 seconds. However, the results may be due to flawed methodology. Because different trigrams were used on each trial, this may have led to interference between items, leading to decreased recall. Also, recalling nonsense trigrams has little relevance to STM tasks in everyday life and therefore lacks mundane realism.
- Marsh et al. (1997) found that if participants weren’t expecting to have to recall information, STM duration was only between two and four seconds, which suggests duration of STM is affected by the amount of time taken to process information.
What is the evaluation for the duration of the STM?
- Reitman (1974) suggested the brief duration of STM is due to displacement; as new information comes into STM it pushes out existing information due to its limited capacity (see Explanations for forgetting, page 76).
- There is little in the way of research evidence considering the STM duration of other forms of stimuli, like visual images.
