Memory: L1-4 Flashcards
Short term memory:
Stores and allows recall of information for a period of several seconds up to 30 seconds without rehearsal. It’s capacity is very limited
Long term memory:
Stores and enables us to recall information from the distant past. It’s capacity is unlimited and it’s duration is potentially a lifetime
Duration:
A measure of how long information can be stored for or how long it lasts
Short term memory duration:
Does not last long. In order to keep information in the STM for more than a few seconds it must be commonly rehearsed to keep it active
Peterson and Peterson (1959):
- 24 undergraduate students were presented with a consonant trigram eg ZFB
- They were then asked to count backwards in threes to stop them repeating/rehearsing the consonant trigram
- After intervals of 3, 6, 9, 12, 18 seconds, Participants had to repeat the trigrams
- This was repeated using different trigrams
Results: Participants could remember about 90% after 3 seconds, 20% after 9 seconds and less than 10% after 18 seconds
Conclusion: information decays quickly when it can be rehearsed. The STM has a maximum duration of 18-30 seconds without rehearsal
Strengths of Peterson and Peterson:
It is a lab experiment, so variables can be tightly controlled eg how many trigrams. This allows the procedure to be repeated to test reliability
Weaknesses of Peterson and Peterson:
It had low ecological validity, as memorising trigrams is not common in daily life
Trigrams presented may have caused confusion - uncertainly if the results gained were due to confusion or forgetting the letters
Bahrick et al (1975):
Tested how well 400 Americans remembered former classmates, by asking on to identity pictures, matching names to pictures and recalling names with no picture clue
Results: after 48 years, 70% accuracy. However, when asked to free recall the classmates names, then accuracy after 48 years was 30%
Conclusion: 30-50 years later, participants could remember classmates, suggesting the LTM can last a life time. If a cue is present, then recall is higher
Strengths of Bahrick et al:
High external validity as it was meaningful material, (making it more useful than Petersons study which uses meaningless trigrams) making it applicable to daily life
Weaknesses of Bahrick et al:
- Natural experiment so the experimenter had less control of the IV, so some of the names may have been rehearsed eg some classmates may still be in touch (confounding variable)
- Only looked at a specific type of information - names. May not be applicable to all forms of memory. Not all LTMs are there for a lifetime
Capacity of memory:
This is a measure of the format in which information is stored in the various memory stores. LTM is potentially unlimited, STM is limited
Jacobs (1887):
Developed the serial digit span technique. The researcher read out 4 digits and the participants repeated back immediately. Digits were added until the participant could not accurately repeat back
Results: on average 9 digits and 7 letters were recalled correctly. The capacity increased with age, possibly due to an increase in brain capacity and/or because people develop strategies eg chunking
Weaknesses of Jacob (1887):
- Lacks ecological validity - listing numbers and repeating them is not a common occurrence
- Previous sequences recalled may have been confused in later trials (confounding variables)
- The study was conducted so long ago extraneous variables eg distractions cannot be calculated
Strengths of Jacob (1887):
Has been repeated many times - suggests the study has validity
Miller (1956):
Reviewed experiments into the capacity of STM concluded that it has a capacity of 7 +/-2 items He also stated that memory could be increased via chunking. Cowan (2001) stated that Miller may have overestimated the capacity of the STM and concluded it was around 4 chunks.
