Memory Flashcards
Capacity of short-term memory (who and what)
Joseph Jacobs. Digit span tasks. P recalls these in order. No. of digits increases each time until p can’t recall the order correctly.
Mean: 9.3 for digits. 7.3 for letters.
Miller: observations of everyday practice, things come in sevens. 5+/-2. Chunking= grouping info into meaningful chunks
Duration of STM
Peterson+Peterson. 24 students 8 trials. Consonant trigrams. Count backwards in 3s to prevent rehearsal.
On each trial they stopped after varying periods of time (retention interval).
After 3 seconds: 80%
After 18 seconds: 3%
Suggests STM duration 18 secs without rehearsal.
Duration of LTM
Bahrick. High school year book photos (cued recall). Recite names of grad class (free recall).
After 15 years: 90% accurate
After 48 years: 70% accurate
Free recall:
15 years: 60%
48 years: 30%
Up to a lifetime!
Baddeley’s study of encoding
Different word lists to 4 groups.
G1: acoustically similar
G2: acoustically dissimilar
G3: semantically similar
G4: semantically dissimilar
Recall immediately or after 20 minutes. .
STM: did worse acoustic. Coded acoustic
LTM: did worse semantically. Coded semantically.
Characteristics of memory evaluation
+ (Baddeley) Identified clear difference between 2 memory stores. Idea has stood test of time. Led to multi store model.
- (Baddeley and Peterson×2) artificial stimuli. Word lists= not everyday life. Although we do sometimes have to remember phone numbers. Lacks external validity.
+ (Bahrick). High external validity. Meaningful memories.
MSM: Sensory Register
Coding: 5 senses, e.g., iconic for visual, echoic for sound.
Duration: less than 1/2 a second
Capacity: Potentially unlimited
Information passes if you pay attention
MSM: Short-term memory
Coding: acoustic
Capacity: 7+/-2
Duration: 18 seconds
Information passes through maintenance rehearsal.
MSM: long term memory
Coding: semantic
Capacity: potentially unlimited
Duration: up to a lifetime
To recall info from LTM, it must be transferred back into STM by a process called retrieval.
Case of HM
Underwent brain surgery for epilepsy when the procedure was still in its infancy. They removed the hippocampus from both sides of his brain. We now know this to be central to memory function.
When his memory was assessed in 1955, he thought the year was 1953 and that he was 27 years old (he was 31).
He had very little recall of the operation and could not form new long-term memories. E.g. would read the same magazine repeatedly.
Performed well on tests kf immediate memory span (STM).
MSM of memory evaluation
☆Research support: STM and LTM are different. Baddeley’s study of encoding. All memory studies.
× artificial stimuli used in memory studies (bar Bahrick’s) which lacks ecological validity.
×more than one STM? KF had amnesia and his recall of digits read out to him was very poor but recall of digits he read himself was better. Further studies showed there could be a store for non-verbal sounds as well.
× Elaborative rehearsal: according to the MSM, the more you rehearse something the more likely it is to transfer to LTM (prolonged rehearsal). Craik and Watkins found that elaborative rehearsal is better.
× oversimplified
The working memory model
Baddeley and Hitch (1974).
Central executive: ‘supervisory’ role. Divides attention to different systems. Limited processing capacity and does not store info.
Phonological loop:
-Phonological store: stores words you hear. Preserves order.
-Articulately process: allows maintenance rehearsal- repeating sounds in loop to keep them in working memory. Capacity: 2 seconds
Visuo-spatial sketchpad:
-visual cache: stores visual data
-inner scribe: records arrangement of objects in visual field
Capacity: 3/4 objects
Episodic buffer: added in 2000. Temporary store. Records events as they happen. Capacity of about 4 chunks. Links to LTM and wider cog processes such as perception.
