Memory - Coding, capacity and duration Flashcards
What does duration mean?
The length of time that information can be stored in memory
What does capacity mean?
The amount of information that can be stored in memory
What does coding mean?
A process by which the sensory information is modified and stored in the brain
What are the different types of memory stores?
Sensory register
STM
LTM
What is the capacity of sensory store?
Very large
What is the capacity of STM?
7 +/- 2 items
What is the capacity of LTM?
Potentially unlimited
Research into capacity: how is STM often assessed?
Digit span task - numbers spanning 3-8 digits, covering all but the first row and moving on if recalled correctly. Digit span is how many digits are recalled correctly
Research into capacity: Jacob’s (1887) research on STM
Ppts. read sequence of letters/numbers and asked to repeat it back immediately. Additional digit added on each subsequent trial to measure STM capacity
Average span for numbers = 9.3
Average span for letters = 7.3
Research into capacity: Miller’s (1956) research on STM
Reviewed psychological research to conclude ‘the magic number for capacity is 7 +/- 2 items’ regardless of whether they’re letters or numbers
Research into capacity: what did Miller suggest about chunking?
Argued capacity for remembering info can be increased if we chunk items together. Linking info and grouping together can increase capacity for STM
What is the duration of sensory store?
Less than 1 second
What is the duration of STM?
18-30 seconds
What is the duration of LTM?
Potentially infinite
Research into duration: Peterson and Peterson (1959) procedure (STM)
On each of 8 trials, 24 uni student ppts. given a consonant trigram (TRX 512) + 3-digit number, asked to recall consonant syllable after intervals of 3,6,9,12,15 or 18s. To prevent rehearsal ppts. had to count back from 3-digit number
Research into duration: findings of Peterson and Peterson (1959) (STM)
After 3 seconds, recall accuracy = 80%
After 9 = 20%
After 18 = less than 10%
Conclusion = duration of STM is less than 18 seconds
Research into duration: Bahrick et al (1975) procedure (LTM)
392, 17-74 year olds from USA. Ppts.’ asked to name 50 students from high school yearbook photos. Asked to list names from graduating class to investigate duration of LTM
Research into duration: Bahrick et al (1975) findings (LTM)
For photos:
Ppts. tested within 15 years of graduation = 90% accuracy
After 48 years = 70% accuracy
For free-recall:
After 15 = 60%
After 48 = 30%
Conclusion = duration of LTM can last a long time
How is information encoded in the sensory store?
Modality specific (encoded in the same way it’s received)
How is information encoded in the STM?
Acoustically
How is information encoded in the LTM?
Semantically
Research into coding: Procedure of Baddeley (1966)
Independent group ppts. shown list of words (acoustically/semantically , similar/dissimilar) and asked to recall in correct order. To test STM, ppts. recalled words immediately after hearing them and to test LTM they recalled words after 20 min interval
Research into coding: Findings of Baddeley (1966)
STM = struggled remembering acoustically similar words when tested immediately
LTM = had no difficulty remembering acoustically similar words after 20 mins
STM = had no difficulty remembering semantically similar words immediately
LTM = struggled remembering semantically similar words after 20 mins
