- Peterson & Peterson (1959)
- Aims & Procedure: 24 students, consonant syllables, verbal rehearsal prevented, there was a retention interval of 3, 6, 9, 12,15, 18 seconds.
- Findings & 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: 1. One limitation of this study is that the stimulus material was artificial. 2. A second limitation is that the study lacked validity because displacement may explain the findings.
1. Miller (1956)
- Aims & procedure:The study is a meta- analysis, things come in sevens, one STM task involved counting dots lashed on a screen.
- Findings & conclusions: People can count 7 but not 15 dots flashed on a screen. It suggests capacity of STM is about 7 times (+2). Chuncking is used to increase capacity.
- Evaluation: 1.one limitition is that Miller may have overestimated the capacity of STM. 2. One strength of the study is that Miller's insights led to everyday applications (generalisability).
Jacobs (1887) Capacity of STM.
- Aims & procedure: developed digit span technique, digits/letters read one at a time. Recall tested and then another digit added until participant can't recall correct order.
- Findings & Conclusions: Mean span for digits is 9.3. Meal span for letters is 7.3. Digit span increased with age, possibly due to chunking.
- Evaluation: 1. One limitation is that it was conducted a long time ago. 2. One strength is that the results are useful in confirming Miller's conclusions.
Baddeley (1966) Encoding in STM and LTM,
- Aims & procedure: Four groups (acoustically/semantically similar/dissimilar. Recall was tested by placing words in right order. STM and LTM tested.
- Findings & conclusions: Acoustically similar words remebered worst for STM. Semantically similar words remembered worst for LTM. This suggests that encoding differs between STM and LTM.
- Evaluation: 1. One limitation of this study was that it used quite artificial stimuli rather than meaningful material. 2. Another limitation of this study is that the LTM memory task wasn't very long term.
Atkinson & Shiffrin (1968)
- Theory: Information processing model diagram. Sensory memory (SM), duration = milliseconds, capacity = very large. Attention to items in SM leads to transfer to STM. STM has limited duration (measured in seconds) and capacity (about 5 chunks) and acoustic encoding. Increasing verbal rehearsal leads to transfer from STM to LTM. LTM has potentially unlimited duration and capacity. Encoding tends to be semantic.
- Evaluation: 1. One strength of MSM is that it is easy totest the predictions of the model experimentally. 2. A second strength of the MSM comes from research support from the case study of HM. Further research comes from brain scans prefrontal cortex is often active when individuals are involved in immediate tasks (i.e. STM) whereas the
hippocampus is active when LTM in individuals is engaged) 4. One limitation of MSM is that it oversimplifies memory processes. 5. A second limitation of the MSM is that…