Short and Long Term Memory

Question 1

Describe coding

Answer 1

• Info stored has to be ‘written’ in memory in some form - sounds, images and meaning
• Baddeley used word lists to test effects of acoustic and semantic similarity on STM and LTM. Found participants had difficulty on STM and LTM. He found that participants had difficulty remembering acoustically similar words in STM but not in LTM, but semantically similar posed little problem for STMs but led to muddled LTMs. Suggests STM is encoded acoustically whereas LTM is encoded

Question 2

Describe capacity

Answer 2

• How much data can be held in a memory store. STM is a limited capacity store while LTM has a potentially unlimited one.
• Jacobs assessed STM capacity using digit span. He found the average span for digits was 9.3 items and 7.3 for letters. He suggested it’s easier to recall digits as there’s only 9 digits compared to 26 letters
• Miller (1965) concluded the span of immediate memory is about 7 items (7 +- 2). He noted that people can count 7 dots flashed onto a screen but not many more, the same is true for musical notes, letters and words. Miller found people can recall 5 words as well as they can 5 letters, we chunk things together and can remember more

Question 3

Describe duration

Answer 3

• LTM may last forever but STM doesn’t last very long, unless you repeat the items.
• Peterson and Peterson studied the duration of STM, using 24 students. Each was tested over 8 trials on each they were given a consonant syllable (THX 512) after a retention interval 3,6,9,12.15 or 18 seconds. During the retention interval they had to count backwards from their 3-digits. On average, they were 90% correct over 3 seconds, 20% correct over 9 seconds and 2% correct after 18 seconds. Suggesting STM has a very short duration, less than 18 seconds, if verbal rehearsal is prevented.
• Bahrick et al tested 400 people of various ages (17-74) on their memory of classmates. A photo-recognition test consisted of 50 photos, some from their high-school yearbook. In a free-recall test they were asked to list the names they could remember of those in their graduating class. Those tested within 15 years of graduation were about 90% accurate in identifying faces. After 48 years, it was 70% for photo recognition. Free recall was about 60% accurate after 15 years, but 30% after 48 years.

Question 4

Give evaluation for research into capacity

Answer 4

• Miller’s original findings haven’t been replicated. Cowan reviewed a variety of studies on the capacity of STM and found that STM is likely to be limited to about 4 chunks. Vogel et al found the capacity of STM for visual info was about 4 items. This means that the lower end of Miller’s range is more appropriate (5). Suggests STM may not be as extensive as was thought, and may depend on the type of info.
• Another criticism is the size of the chunk affects how many chunks you can remember. Simon found that people had a shorter memory span for larger chunks such as 8-word phrases, than smaller chunks, like one-syllable words. This supports the view that STM has a limited capacity and refines our understanding

Question 5

Give evaluation for research into duration

Answer 5

• There are issues with the methodology. The task and setting don’t reflect memory in real life. Remembering trigrams in a controlled setting is not something we typically have to remember. The stimuli (trigrams) aren’t stimuli we have to remember in real life either. Suggests that Petersons’ research lacks both ecological validity and mundane realism. Prevents us from generalising to understand typical day-to-day duration of STM.
• STM results may be due to displacement not decay. In the Petersons’ study, participants were counting the numbers in their STM which may displace the memory of the syllables. Reitman used auditory tones instead of numbers so that displacement wouldn’t occur and found duration of STM was longer, suggesting forgetting was due to displacement.

Question 6

Give evaluation for coding

Answer 6

• Baddeley’s research into coding of LTM may not have actually tested LTM. Baddeley tested STM by asking participants to recall a word list immediately after hearing it. LTM was tested by waiting 20 minutes. It’s questionable as to whether this is really testing LTM. Casts doubts on the validity of Baddeley’s research .
• STM may not be exclusively acoustic. Brandimote et al found participants used visual coding in STM if they were given a visual task (pictures) and prevented from verbal rehearsal tasks in the retention interval before performing a visual recall task. Furthermore, in the case study of KF, his STM was visual as he could recall written words but not when they were said to him. Normally, we ‘translate’ visual images into verbal codes in STM, but as rehearsal was prevented, participants used visual codes. Suggesting, STM isn’t purely acoustic.
• LTM may not be exclusively semantic. Frost showed that long-term recall was related to visual as well as semantic categories. Nelson and Rothbart found evidence of acoustic coding in LTM. Suggesting LTM isn’t coded simply semantically but may vary according to circumstances