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 a limitation of the research into capacity? - Miller’s potential overestimation for STM capacity
===> Cowan (2001) reviewed research and concluded STM is closer to 4 chunks of info, which may be a more appropriate ‘magic number’ than 7. Important to consider memory can be influenced by individual differences so challenging to draw universal conclusion. Samples used in populations for respective research could have differed and explained different findings
What is a limitation of the research into capacity? - Miller’s absence of specification regarding size of chunk
===> Simon (1974) discovered individuals have a smaller STM capacity when dealing with larger chunk, such as 8-word phrases, compared to single syllable words. Suggests Miller’s explanation alone isn’t sufficient to fully account for STM capacity as it’s too vague. Despite this, research supports perspective that STM does have limited capacity
What is a limitation of the research into capacity? - Jacob’s capacity estimate isn’t uniform for everyone
===> Jacob’s (1887) research demonstrated digit span recall consistently increased with age. On average, 8 year olds remembered 6.6 digits whilst 19 year olds remembered 8.6. Suggests STM capacity increases with age or develop better strategies to enhance digit span, not mentioned in their findings. Caution should be taken to generalise findings, individual differences influence the STM capacity
What is a limitation of the research into capacity? - Lack of ecological validity
===> Studies by Jacobs (1887) and Miller (1956) conducted in artificial settings and used meaningless words, numbers and objects to test memory. Doesn’t reflect how memory is used in the real world. In everyday life, memory carries more personal significance so lack of mundane realism means results only generalised to real-world scenarios
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 photo. 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
What is a limitation of research into duration? - Methodology of Peterson and Peterson (1959)
===> Might not have been measuring trace decay but instead displacement, lowering construct validity. Ppts. asked to engage in distraction task of counting backwards in 3s and 4s so this complex task could have overridden trigrams and resulted in displacement rather than solely preventing rehearsal. Reitman (1974) conducted study using auditory tones instead of counting back so displacement wouldn’t occur. Findings suggest STM duration is longer
What is a limitation of research into duration? Peterson and Peterson (1959) questionable ecological validity
===> Stimulus material of consonant trigram used in task was highly artificial so lacked mundane realism as it didn’t reflect real-life examples of memory. People usually required to remember personal events which have greater personal significance than nonsensical syllables. However, in certain situations, we do remember meaningless information like phone numbers, car regs and postcodes so could be representative
What is a strength of research into duration? Bahrick et al (1975) higher ecological validity than P+P
===> As ppts.’ memory was tested on their own high school peers, mundane realism enhances generalisability of results. However, introduces confounding variables as some ppts. may remember their friends or classmates better than those who didn’t see each other often. Argued that Bahrick shows high ecological validity but low internal so should be noted when generalising findings
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
What’s a strength of research into coding? - Demonstrate existence of separate memory stores
===> Baddeley’s (1966) research is fundamental in evidencing that info is encoded acoustically in the STM and info is encoded semantically in the LTM. This proves they’re separate and distinct memory stores and played a crucial role in the development of the MSM. The finding of separate memory stores has consistently withstood the test of time, making it a reliable find
What’s a limitation of research into encoding in the STM? - Presence of contradictory research evidence
===> Brandimonte et al (1992) discovered ppts. used visual coding in the STM when engaged in a visual task and were prevented from verbal rehearsal before having to visually recall info. Nelson and Rothbart (1972) found evidence of acoustic coding in LTM, indicating encoding isn’t solely acoustic in STM or semantic in LTM. Generalisability of Baddeley’s findings to all types of learning isn’t equally applicable
What’s a limitation of Baddeley’s research into coding? - Lack of ecological validity
===> Research was conducted in a lab setting so it’s hard to generalise findings to real-world contexts. Baddeley used meaningless words to test ppts. recall which doesn’t reflect how memory is used in real life. It carries more personal meaning in reality. His task lacked mundane realism so mightn’t accurately reflect how memory functions in real life
