Memory - Short and Long Term Memory

Question 1

Definition of capacity

Answer 1

A measure of how much can be held in memory. It is represented in terms of bits of informations, such as a number of digits. Short term memory (STM) has a limited capacity, LTM has a potentially infinite capacity.

Question 2

Studies of capacity

Answer 2

Jacobs - used the digit span technique to assess STM capacity. Found that the average span for digits was 9.3 items and 7.3 for letters (only 9 digits compared to 26 letters)

Miller - people remember about 7 chunks, give or take 2. He discovered ‘the magic number 7 plus or minus 2’

Question 3

Evaluation of capacity

Answer 3

Cowan - 4 chunks probably the limit, same for visual information (Vogue et al.)
Simon - size of the chunk affects recall.
Jacobs - individual differences - 19-year-olds have longer digit span than 8-year-olds.

Question 4

Definition of duration

Answer 4

A measure of how long a memory lasts before it is no longer available.

Question 5

Studies of duration

Answer 5

Peterson and Peterson - STM - three letter ‘trigrams’ or 3 digit numbers given, asked to recall, count backwards in 3s to prevent rehearsal - 90% recalled correctly over 3 seconds, 20% after 9, 2% after 18. Suggested that the STM has a very short duration if rehearsal is prevented.

Bahrick et al. - LTM - 400 people ages 17-74 tested on memory of their classmates (photo recognition). Free-recall of as many names they could remember from graduation class. Within 15 years of graduation 90% were accurate in identifying faces, after 48 years this declined to 70%. Free recall was 60% after 15 years, 30% after 48.

Question 6

Evaluation of duration

Answer 6

Peterson and Peterson:

• trigrams lack ecological validity, however we need to remember post codes in real life etc
• forgetting due to displacement from verbal counting. Reitman used auditory tones to prevent rehearsal to prevent rehearsal and found that the duration of the STM was longer.
• Nairne et al. Found the duration for STM to be as long as 96 seconds.

Question 7

Definition of coding

Answer 7

The way information is changed so that it can be stored in memory. Information enters the brain via the senses. It is then stored in various forms, such as pictures, sounds, and meanings.

Question 8

Studies of coding

Answer 8

Baddeley -

• 2 lists of words, 1 acoustically similar but semantically different, 1 semantically similar but acoustically different.
• participants had difficulty remembering acoustically similar words in STM but not in LTM, whereas semantically similar words were easily to remember in STM but got muddled in LTM.
• suggests that the STM is largely encoded acoustically, and the LTM is largely encoded semantically.

Question 9

Evaluation of coding

Answer 9

Baddeley:
-tested LTM by waiting 20 minutes - was this LTM?
Brandimote et al.:
-participants who used visual coding in STM and were prevented from verbally rehearsing used visual codes.
Wickens et al.:
-sometimes the STM uses semantic code.
LTM not just semantic:
-Frost found evidence for visual coding.
-Nelson and Rothbart found evidence for acoustic coding.