Duration

Peterson and Peterson (consonant syllables)

Aims and procedure

• 24 students, 8 trials each
• Consonant syllable, verbal rehearsal prevented
• Retention interval of 3,6,9,12,15,18 seconds 

Findings and Conclusions

• After 3 seconds, recall was about 80% 
• After 18 seconds, recall was about 3%
• This suggests that STM has duration of less than 18 seconds if verbal rehearsal is prevented 

Evaluation

• One limitation of this study is that the stimulus material was artificial - trying to memorise consonat syllables does not reflect real life memory activites - could lack ecological validity 
• A second limitation is that the study lacked validity because displacement may explain the findings

Bahrick et al - face recognition test 

Aims and procedure 

• nearly 400 p's, aged 17-74
• high school yearbook 
• recognition test of faces or free recall of names 

Findings and conclusions 

• face recogniton was 90% accurate after 15 years
• declined to 70% after 48 years
• free recall was 60% accurate after 15 years 

Evaluation

• one limitation of this study is that rehearsal may explain their results 
• one strength of this study is that it has high ecological validity 

Miller - 7 +-2

Aims and procedure

• this study is a review of other research 
• things come in sevens
• one STM task involved counting dots lashed on a screen 

Findings and conclusions 

• can count 7, but not 15 dots flashed on a screen
• suggests capacity of STM is about 7 items (+2)
• chunking is used to increase capacity 

Evaluation

• one limitation of this study is that Miller may have overestimated the capacity of STM 
• one strength os this study is that Miller's insighs led to everyday applications 

Jacobs

Aims and procedure

• developed digit span technique 
• digits/letters read one at a time 
• recall tested and then another digit added until P's can't recall correct order

Findings and conclusions

• mean span for digits is 9.3
• mean span for letters is 7.3
• digit soan increased with age, possibly due to chunking 

Evaluation 

• one limitation of this study is that it was conducted a long time ago
• one strength of this study is that the results are useful in confriming Miller's conclusions 

Baddeley 

Aims and procedures 

• four groups (acoustically/semantically/similar/dissimlar)
• recall was tested by placing words in right order
• STM and LTM tested

Findings and conclusions

• acoustically similar words remmebered worst for STM
• semantically similar words remembered worst for LTM
• suggests that encoding differs between STM and LTM

Evaluation 

• one limiation of this study was that it used quite artificial stimuli rather than meaningful material
• another limitaion of this study is that the LTM memory task wasn't very long term 

Atkinson and Shiffrin

Theory

• Sensory memory, duration = milliseconds, capacity = very large 
• attenton to items in SM leads to transfer to STM
• STM has limited duration (measured in seconds) and capacity (about 5 chunks) and aciustic encoding
• increasing verbal rehearsal leads to transfer from STM to LTM
• LTM has potentially unlimited duration and capacity. Encoding tends to be semantic.

Evaluation

• one strength of the MSM is that it is easy to test the predictions of the model experimentally
• a second strength of the MSM is that further research support comes from brain scans
• a limitation of the MSM is that it originally ignored the importance of elaborative rehearsal

Baddeley and Hitch

Theory

• WMM is a detailed explanantion of STM
• central executive allocates slave systmes
• phonological loop (first slave system) consists of phonological store and articulatory process
• Visuo-spatial sketchpad (secind slave system) - stores visual/spatial information when required
• episodic buffer (third slave system) - temporsry storage
• dual task performance illustrates WMM

Evaluation