Describe and evaluate research into Coding, capacity and duration

What is coding?

Coding refers to the format or ‘type’ of information which is stored in each memory store.

Coding is acoustic in short-term memory, and semantic in long-term memory, as demonstrated by Baddeley (1966),

who found that more mistakes are made when recalling acoustically-similar words straight after learning them, whilst more mistakes are made when recalling semantically-similar words 20 minutes after learning them (LTM recall)

What is capacity?

Capacity refers to the volume of information/data which can be kept in any memory store at any one time.

For example, the capacity of STM is thought to be 7 +/- 2 items (Miller), whilst the capacity of LTM is unlimited.

This is based on Miller’s idea that things come in groups of 7 (e.g. 7 days of the week), suggesting that we are predisposed to remembering this quantity and that such a ‘chunking’ method can help us recall information.

Jacobs also demonstrated that the mean letter span was 7.3 and the mean digit span was 9.3 (i.e. the number of letters or digits we can recall after increasing intervals).

What is duration?

Duration refers to the amount of time that information can be stored in each memory store. The duration of STM is 18-30 seconds, as demonstrated by Petersen et al (1959), who found that increasing retention intervals decreased the accuracy of recall of consonant syllables in 24 undergraduates, when counting down from a 3 digit number (preventing mental rehearsal). The duration of LTM is unlimited, as shown by Bahrick et al (1975), who found that photo recognition of graduating classmates of the 396 participants decreased from 90% to 70% between 15 years and 46 years of graduating.

-A key issue with historical psychological research, particularly concerning Jacobs, is the lack of standardisation and appreciation of scientific methods.

For example, the current laboratory experiment methodology produces highly reliable and valid data through controlling and so removing the effects of extraneous and confounding variables.

The same is unlikely to be said of Jacobs, where confounding variables such as a noisy room or difficult word lists, may have had a greater influence on accuracy of recall, leading to unreliable results.

+A particular strength of Bahrick et al’s 1975 study is the use of meaningful stimuli, and a methodology which is high in mundane realism.

This suggests that the findings have high ecological validity because they can be easily generalised to real-life, due to the stimuli reflecting those which we would often try to learn and recall in our day to day lives: information with personal and meaningful value!

-Conversely, the key issues with the Petersen et al and Miller et al studies is that they feature methodologies with low mundane realism, thus producing findings with little ecological validity.

This is due to the use of artificial stimuli which has little personal meaning to the participants, and so does not accurately reflect everyday learning experiences. This therefore limits the generalisability of such findings.

— More recent research has suggested that Miller may have over-exaggerated the capacity of STM, and that the capacity is more similar to 4 chunks as opposed to the original 5-9 limit.

This may reflect the outdated methodologies adopted by Miller and specifically, the lack of control over confounding variables which may have contributed to this inaccurate estimate