Memory: Duration, Capacity + Encoding

Duration of STM

Who: Peterson & Peterson: Trigram recall test

Procedure: 24 students, asked to recall nonsense trigrams (AFC), interfrence task of counting back in 3's (330,337,334). Asked to recall trigram, time increased 3 seconds each time upto 18 seconds

Findings: 90% recalled trigram after 3 seconds interval, 2% after 18 seconds

Conclusions: STM duration lasts upto 18 seconds

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AO2: lacks mundane realism, low ecological valdity, cannot be genrelised, high internal valdity, sample bias; 24 psychology students, age bias. 

Duration of LTM

Who: Bahrick et al: Yearbook recall

Procedure: Four tests: 1. Free recall of names, 2. Photo recognition, 3. Name recognition and 4. Name to photo recognition 

Findings: 90% of face and name recognition after 15 years, dropped to 80% for name and 40% for face after 48 years. Free recall was 60% accurate after 15 years, then 30% after 48 years

Conclusions: Recongntion is better than recall

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AO2: high mundane realism, high ecological validity, low external validty, cannot be controlled, 17 year olds more likley to remember faces and names, 

Capacity of STM

Who: Joeseph Jacobs: Digit span test

Procedure: Asked participants to recall digits, increasing the digit number by one each time. 

Findings: That average digit span recall was 9.3, whilst letter recall was 7.3. Also adults were better (19 year old) had 8.6 span, whilst 8 year old had 6.6 digit span.

Conclusions: Capacity of STM is between 5-9 pieces of information 

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AO2: low mundane realism, high internal valdity, low external validty, demand characteristics 

Who: Baddely: acoustic and semantic recall

Procedure: 4 lists of words: acoustically similar and dissimilar, semantically similar and dissimilar. 

Findings: People were able to recall acoustic words in STM, and recall semantic (meaning of) words using LTM. 

Conclusions: STM: Acoustic (sound) LTM: Semantic (meaning)

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AO2: low mundane realsim, demand charcteristics, high internal validty