4.1.2 Duration

Question 1

Short term memory

Answer 1

Margaret and Lloyd Peterson –
Peterson and Peterson
1959

Question 2

Short term memory method

Answer 2

Peterson and Peterson
Tested 24 students in eight trials each
On each trial the students were given a consonant syllable (e.g., YCG, JWG) to remember
They were then given a 3-digit number which they had to count backwards from until they were told to stop
This backwards counting is to prevent mental rehearsal
On each trial, they were told to stop after varying periods of time – 3,6,9,12,15,18 seconds (retention interval)

Question 3

Short term memory - results

Answer 3

After 3 seconds, average recall was about 80%
After 18 seconds, average recall was about 3%
Peterson and Peterson’s findings suggested that STM memory duration may be about 18 seconds, unless we repeat the information over and over (verbal rehearsal)

Question 4

Long term memory

Answer 4

Harry Bahrick et al.
(1975)

Question 5

Long term memory - method

Answer 5

Studied 392 American participants aged between 17 and 74
High school yearbooks were obtained
Recall was tested in various ways:
Photo-recognition test consisting of 50 photos, some from their yearbook
Free recall test where participants recalled all the names of their graduating class

Question 6

Long term memory - results

Answer 6

Participants tested with 15 years of graduation were about 90% accurate in photo recognition
After 48 years, recall declined to about 70% for photo recognition
Free recall was less accurate than recognition – about 60% after 15 years, dropping to 30% after 48 years
This suggests that LTM may last up to a lifetime for some material

Question 7

Evaluation - strengths

Answer 7

Bahrick et.al has high external validity
This is because meaningful memories were investigated (names and faces)
When LTM studies were conducted with meaningless pictures to be remembered (Shepard 1967), recall rates were lower
Suggesting Bahrick et.al’s findings reflect a more ‘real’ estimate of the duration of LTM

Question 8

Evaluation - weaknesses

Answer 8

One limitation is that Peterson’s stimulus material was artificial (YDW)
However, the study isn’t completely irrelevant as we do need to remember some meaningless material (some phone numbers)
Recalling consonant syllables does not reflect most everyday memory
Meaning this study lacked external validity