Outline and evaluate research into capacity, duration and coding:
AO1: coding
● Coding: the format in which our memories are stored.
Research into coding - Baddeley: gave four groups of 72 participants different lists of words
to remember:
1. Acoustically similar 2. Acoustically dissimilar
2. Semantically similar 3. Semantically dissimilar
- Tested recall in correct order either straight away (STM) or after 20 minutes (LTM).
- STM recall was worse with the acoustically similar words but better with the
acoustically different words.
- LTM recall was worse with the semantically similar words but better with semantically
different words.
Findings:
- Information is coded acoustically in STM.
- Information is coded semantically in LTM.
AO3: coding
Strength: Controlled methods, eg: ppts all received standardised instructions in a lab setting,
scientific so allows the researcher to objectively establish a cause and effect relationship
how memory is coded, can be used with various participants, will show consistent findings,
easily replicable, increases reliability, can be used appropriately as an explanation of coding.
Weakness: Artificial stimuli, eg: used word lists that had no personal meaning to the ppts,
doesn’t consider the fact that people may use semantic coding to help them remember info,
cautious when generalising findings to different memory tasks or real-life application,
decreases external validity, cannot appropriately explain how information is coded in STM.
AO1: capacity
● Capacity: the amount of info that can be held in a memory store
● STM = finite, limited capacity // LTM = unlimited
● LTM = Bahrick’s study - unlimited capacity
● Research on STM capacity - Jacobs: digit span test
- Ppts given, eg: 4 digits to recall, then 5 digits and so on until they can’t recall all
correctly.
Findings:
- Mean span for digits = 9.3, mean span for letters = 7.3 // 5-9 items
● Research on STM capacity - Miller: memory and chunking
Findings:
- Magic number = 7±2 chunks, chunking increases amount that can be held in memory
, AO3: capacity
Weakness: Jacobs study. Lack of validity, eg: conducted a long time ago, participants may
have been distracted while they were being tested so they didn’t perform as well as they
might have, results may not be valid as there were confounding variables that were not
controlled, decreasing temporal validity.
Weakness: Miller’s study. Overestimated the capacity of STM, eg: Cowan reviewed other
research and concluded that the capacity of STM was only about four chunks, lower end of
Miller’s estimate (five items) is more appropriate than seven items, decreasing reliability.
AO1: duration
● Duration: the length of time information can be held in memory
Research into LTM duration - Bahrick et al’s yearbook study
- LTM= Bahrick et al. 392 ppts aged 17-74
- Used their high school yearbook to test memory, either tested on photo-recognition
(50 pics, some from school, others not) or through free recall (simply naming
students from their class).
- Ppts tested within 15 years of graduation: 90% accurate photo- recognition and 60%
free recall. After 48 years: 70% photo-recognition, 30% free recall.
Findings:
- LTM is unlimited in duration / unlimited recall
Research into STM duration - Peterson & Peterson
- 24 students tested on eight trials, for each trial, ppts were briefly shown a trigram
(three letter nonsense word - eg: SLM).
- Trigram taken away and ppts were then told to count backwards in 3s from a 3 digit
number until told to stop to prevent rehearsal.
- For each of the trials, length of time counting backwards was different - either
3,6,9,12,15 or 18 secs, the time was called the retention interval.
- Ppts then asked to recall the trigram, found 80% correct recall of the trigram after 3
secs delay, but that recall dropped as the delay got longer, at 18 secs, very few
trigrams were recalled correctly.
Findings:
- STM duration is 18-30 seconds - limited
AO3: duration
Strength: Bahrick et al. High levels of ecological validity, eg: this study included real life
meaningful memory activities, reflects memory of real life events, the findings into the
duration of LTM can be generalised to everyday human memory, increases validity.
Weakness: Peterson & Peterson Artificial materials, eg: consonant syllables,
unrepresentative of real life memory activities, cannot use their findings to understand the
true duration of memory and how it works in the real world as we remember more
meaningful things like faces in the short term, low in ecological validity and low in
explanatory power.
AO1: coding
● Coding: the format in which our memories are stored.
Research into coding - Baddeley: gave four groups of 72 participants different lists of words
to remember:
1. Acoustically similar 2. Acoustically dissimilar
2. Semantically similar 3. Semantically dissimilar
- Tested recall in correct order either straight away (STM) or after 20 minutes (LTM).
- STM recall was worse with the acoustically similar words but better with the
acoustically different words.
- LTM recall was worse with the semantically similar words but better with semantically
different words.
Findings:
- Information is coded acoustically in STM.
- Information is coded semantically in LTM.
AO3: coding
Strength: Controlled methods, eg: ppts all received standardised instructions in a lab setting,
scientific so allows the researcher to objectively establish a cause and effect relationship
how memory is coded, can be used with various participants, will show consistent findings,
easily replicable, increases reliability, can be used appropriately as an explanation of coding.
Weakness: Artificial stimuli, eg: used word lists that had no personal meaning to the ppts,
doesn’t consider the fact that people may use semantic coding to help them remember info,
cautious when generalising findings to different memory tasks or real-life application,
decreases external validity, cannot appropriately explain how information is coded in STM.
AO1: capacity
● Capacity: the amount of info that can be held in a memory store
● STM = finite, limited capacity // LTM = unlimited
● LTM = Bahrick’s study - unlimited capacity
● Research on STM capacity - Jacobs: digit span test
- Ppts given, eg: 4 digits to recall, then 5 digits and so on until they can’t recall all
correctly.
Findings:
- Mean span for digits = 9.3, mean span for letters = 7.3 // 5-9 items
● Research on STM capacity - Miller: memory and chunking
Findings:
- Magic number = 7±2 chunks, chunking increases amount that can be held in memory
, AO3: capacity
Weakness: Jacobs study. Lack of validity, eg: conducted a long time ago, participants may
have been distracted while they were being tested so they didn’t perform as well as they
might have, results may not be valid as there were confounding variables that were not
controlled, decreasing temporal validity.
Weakness: Miller’s study. Overestimated the capacity of STM, eg: Cowan reviewed other
research and concluded that the capacity of STM was only about four chunks, lower end of
Miller’s estimate (five items) is more appropriate than seven items, decreasing reliability.
AO1: duration
● Duration: the length of time information can be held in memory
Research into LTM duration - Bahrick et al’s yearbook study
- LTM= Bahrick et al. 392 ppts aged 17-74
- Used their high school yearbook to test memory, either tested on photo-recognition
(50 pics, some from school, others not) or through free recall (simply naming
students from their class).
- Ppts tested within 15 years of graduation: 90% accurate photo- recognition and 60%
free recall. After 48 years: 70% photo-recognition, 30% free recall.
Findings:
- LTM is unlimited in duration / unlimited recall
Research into STM duration - Peterson & Peterson
- 24 students tested on eight trials, for each trial, ppts were briefly shown a trigram
(three letter nonsense word - eg: SLM).
- Trigram taken away and ppts were then told to count backwards in 3s from a 3 digit
number until told to stop to prevent rehearsal.
- For each of the trials, length of time counting backwards was different - either
3,6,9,12,15 or 18 secs, the time was called the retention interval.
- Ppts then asked to recall the trigram, found 80% correct recall of the trigram after 3
secs delay, but that recall dropped as the delay got longer, at 18 secs, very few
trigrams were recalled correctly.
Findings:
- STM duration is 18-30 seconds - limited
AO3: duration
Strength: Bahrick et al. High levels of ecological validity, eg: this study included real life
meaningful memory activities, reflects memory of real life events, the findings into the
duration of LTM can be generalised to everyday human memory, increases validity.
Weakness: Peterson & Peterson Artificial materials, eg: consonant syllables,
unrepresentative of real life memory activities, cannot use their findings to understand the
true duration of memory and how it works in the real world as we remember more
meaningful things like faces in the short term, low in ecological validity and low in
explanatory power.
