long term & short term memory

what is memory?

the process by which we retain information about events that have happened in the past

what is short-term memory?

your memory for immediate events, measured in seconds and minutes

what is long-term memory?

your memory for events that have happened in the past

what is the duration of LTM?

potentially unlimited in length

what is the duration of STM?

very short <18s

what is the capacity of STM?

7 + or - 2

what is the capacity of LTM?

potentially unlimited

how is STM encoded?

acoustically

how is LTM encoded?

semantically

what does acoustic encoding mean?

through sound

what does semantic encoding mean?

through meaning

what is the key study to support STM’s capacity?

jacobs

what was jacob’s procedure?

• used digit span

what did jacobs find?

the average span was 9.3 digits and 7.3 letters

what did jacobs suggest about the difference between digits and letters?

it was due to there only being 9 digits and 26 letters

who found that 7 + or - 2 is the span of STM?

miller

what is chunking?

the ability to recall 5 words as easily as 5 letters

who argued that the magic number was 4?

cowan

what is the key study to support duration of STM?

peterson & peterson

what was peterson & peterson’s procedure?

• 24 students

• 8 trials

• each pp was given a consonant syllable and 3 digits e.g., THX 512

• pps were asked to recall about intervals increasing from 3 - 18 seconds while counting back from their number in 3s

what were the results of peterson & peterson’s research?

• pps were 90% correct after 3 seconds

• 20% correct after 9 seconds

• 2% correct after 18 seconds

what did peterson & peterson conclude?

STM has a short duration if verbal rehearsal is prevented

what is the key study for duration of LTM?

bahrick et al

what was bahrick’s procedure?

• tested 400 people aged 17+ on memory of classmates

• photo recognition test with 50 photos and a free recall test

what did bahrick find?

• pps who graudated within 15 years scored 90% when identifying faces and 60% in free recall

• pps who graduated 47+ years after were 70% in photos and 30% in free recall

who is the key study for encoding in STM & LTM?

baddeley

what was baddeley’s procedure?

• used word lists to test the effects of acoustic and semantic similarity

what were baddeley’s findings?

• pps struggled to remember acoustically similar words in STM

• pps struggled to remember semantically similar in LTM

• and vice versa

what did baddeley conclude?

STM is largely encoded acoustically whereas LTM is largely encoded semantically

what are the criticisms of research into the capacity of STM and LTM?

• the capacity of STM may be even more limited - cowan (2001)

• the size of the chunk affects how many chunks one can remember - simon (1974)

• individual differences - STM differs between people

what are the criticisms of research into the duration of STM and LTM?

• the testing for STM is artifical as memorising consonant syllables is not reflective of everyday life

• STM results may be due to displacement when counting

what are the criticisms of research into encoding of STM and LTM?

• baddeley may not have tested LTM as he only waited 20 minutes

• STM sometimes uses visual or semantic coding (brandimote et al (1992) and wickens et al (1976))

• LTM may use visual and acoustic coding (frost (1972) and rothbart (1972))