Lesson 1-2 LTM and STM

Question 1

Short term memory

what it does and for how long

Answer 1

• stores and allows the recall of information for up to 30 seconds without rehearsal
• very limited capacity

Question 2

Long term memory

Answer 2

• stores and enables us to remember information from the more distant past
• unlimited capacity, duration is potentially a lifetime

Question 3

Duration

Answer 3

Measure of how long information can be stored for or how long it lasts

Question 4

Short term memory duration

Answer 4

• don’t last long
• in order to keep information in our STM for more than a few seconds, we will commonly rehearse it to keep it active
• study to support by Peterson and Peterson

Question 5

Peterson and Peterson (1959) study for STM duration

procedure, results, conclusion

Answer 5

1) 24 undergraduate pps were presented with a consonant trigrams (3 random consonants) e.g
ZBF
2) then asked to count backwards in threes to stop them rehearsing the consonants
3) after intervals of either 3, 6, 9, 12 ,15 or 18 seconds participants had to stop counting and repeat the trigram
4) this was repeated using different trigrams

Results: pps could remember about 90% of trigrams after 3 seconds, 20% after 9 seconds, and less than 10% after 18 seconds
Conclusion: information decays quickly when it is not rehearsed and the maximum STM duration is about 18 seconds

Question 6

Strengths of Peterson and Peterson study

Answer 6

• it is a lab experiment where variables can be tightly controlled e.g. for how long trigrams are presented
• procedure can also be replicated to see if the results are reliable e.g. nonsense trigrams can be repeated on lots of pps over time and the duration of STM can be tested to see if it has changed over time

Question 7

Weaknesses of Peterson and Peterson study

consonant trigram experiment

Answer 7

• trigrams are unrealistic things to remember and therefore the experiment has low ecological validity
• trigrams presented in earlier trials may have caused confusion or interference when pps came to remember the trigrams in later trials so we are not sure whether the results gained from the pps were due to them forgetting the trigrams or being confused due to interference- this may question how the duration of STM was tested

Question 8

Bahrick et al (1975)

Answer 8

They tested how well 400 American participants (17-74 years old) could remember their former classmates by asking them to identify pictures, matching names to pictures and recalling names with no picture cue. Was carried out after 48 years since school.

Linking name to face- 70% accuracy
Free recall names- 30% accuracy

30-50 years on, pps could still remember their classmates showing that LTM memories can last a lifetime. Also showed that individuals cannot immediately access all information stored in their LTM and may need cues suggesting cues are often needed for higher retrieval.

Question 9

Strengths of Bahricks experiment

Answer 9

• has high external validity because the researchers investigated meaningful material- therefore the study has higher ecological validity than Peterson and Peterson’s study which uses trigrams
• allows us to give a better estimate of the duration of LTM due to the meaningful material used to test it

Question 10

Weaknesses of Bahricks study

Answer 10

• it is a natural experiment so the experimenter had less control of the IV thus its likely some of the names had since been rehearsed e.g. if classmates were still in touch which would be a confounding variable, invalidating the results
• it only looked at specific type of information- names of classmates which is not particularly meaningful and regularly rehearsed

Question 11

Capacity of memory

Answer 11

This is a measure if the format in which information is stored in the various memory stores i.e. how much information can be stored or held. LTM has a potentially unlimited capacity, whilst STM has a very limited capacity.

Question 12

Jacob’s capacity of the STM study

Answer 12

• measured by Jacob’s (1887) who developed the serial digit span technique
• researcher read out 4 digits and pps asked to repeat it back immediately, more digits added until participant could not repeat back the digit string accurately
• on average about 9 digits and 7 letters were correct recalled
• capacity increased with age during childhood (avg digit span for 8 year olds was 6)
• may be because there is a gradual increase in brain capacity and/or because people may develop strategies to improve their digit span, such as chunking
• 9 digits, 26 letters so digits may have been easier to recall

Question 13

Evaluation of Jacobs research

Answer 13

• one problem is that is lacks ecological validity , more meaningful info may be recalled better, so STM may have an even greater capacity
• it could be that previous sequences recalled by pps may have confused them in later trials so we dont know if that factor became a confounding variable
• due to how long ago it was conducted, we cannot be sure that extraneous variables were controlled such as pps IQ levels
• the study has since been repeated and the same results have been found suggesting the study does have validity