1.5 coding, capacity, duration in STM + LTM

what does coding mean in memory?

coding is the way information is stored in memory — either acoustically, visually or semantically.

what did baddeley (1966) find about coding in STM and LTM?

he gave participants word lists that were acoustically or semantically similar.

• stm: confused similar-sounding words → coded acoustically.

• ltm: confused similar-meaning words → coded semantically.

what does capacity mean in memory?

is how much information can be held in memory at one time.

what did jacobs (1887) find about stm capacity?

used a digit span test.

average span: 9.3 for numbers, 7.3 for letters.

stm has a limited capacity of around 7 ± 2 items. (MILLER 1957)

what did miller (1956) find about stm capacity?

found stm can hold 7 ± 2 chunks of information — known as the “magic number 7”.

people can increase capacity by chunking information.

evaluate baddeley’s research on coding

✔ showed clear difference between stm and ltm coding.

❌ used artificial material (word lists) — lacks realism.

❌ real-life memories may use semantic coding even in stm.

evaluate jacobs and miller’s studies on capacity.

✔ research supports stm is limited.

❌ old studies — lack control and standardisation.

❌ capacity may vary depending on age and strategy use.

what does duration mean in memory?

duration is how long information can stay in a memory store before being forgotten.

what did peterson and peterson (1959) find about stm duration?

participants remembered trigrams while counting backwards to stop rehearsal.

after 3 seconds: 80% recall. after 18 seconds: <10% recall.

stm duration is about 18–30 seconds without rehearsal.

evaluate peterson and peterson’s study on duration.

✔ high control, reliable procedure.

❌ artificial task (trigrams), low ecological validity.

❌ may have tested displacement, not decay.

what did bahrick et al. (1975) find about ltm duration?

tested 392 americans on high school yearbooks.

after 15 years: 90% accuracy (photo recognition).

after 48 years: 70% accuracy.

LTM can last a lifetime.

evaluate bahrick et al.’s study on ltm duration.

✔ high ecological validity, real-life memories.

✔ large sample, reliable results.

❌ confounding variables — participants may have rehearsed memories.

summarise differences between stm and ltm.

feature	stm	ltm
coding	acoustic	semantic
capacity	7 ± 2 items	unlimited
duration	18-30 seconds	lifetime

what do clive wearing and hm show about stm and ltm?

both had damaged ltm but normal stm, showing stm and ltm are separate stores, supporting the multi-store model.

how does rehearsal affect memory transfer?

maintenance rehearsal keeps info in stm, prolonged rehearsal moves it to ltm. this links to the multi-store model by atkinson and shiffrin (1968).