Miller (1956)

Aim:
To investigate the capacity of short term memory

Method:
- Participants counted a number of dots flashed onto a screen

Results:
- Participants could recall about 7 items
      - Participants would recall the same number of items for letters/numbers/words

Conclusion:
 - Short term memory holds 7±2 items
 - People chunk things together in order to retain more information

Evaluation:
- A variety of studies show that short term memory is limited to just 4 chunks
      - Cowan (2001)
- When tested on purely visual information it was found that 4 items were the limit
      - Vogel et al. (2001)
- Simon (1974) found that the size of the chunks affect the capacity of STM
      - Larger chunks (such as phrases) mean a shorter span
      - Smaller chunks (such as letters) mean a longer span

Peterson and Peterson (1959)

Aim:
To investigate the duration of short term memory

Method:
- they enlisted 24 students attending their university
- they used a consonant syllable and 3 numbers (e.g. WRT 637)
      - this was done so that they were not meaningful/memorable
- participants were asked to count backwards for intervals of time
      - prevents rehearsal of the syllable
- they used different retention intervals (e.g. 3, 9, 12, 18 seconds)

Results:
- 90% could recall after 3 seconds
- 2% could recall after 18 seconds

Conclusion:
the duration of short term memory is 20 seconds max

Evaluation:
- the participants knew that they needed to recall after a period of time
      - Marsh et al. (1997)
            - participants were not expecting to recall they forgot the syllable after 2 seconds
            - suggests that STM is much shorter
- Peterson and Peterson were only studying one type of memory
      - words and syllables
      - real-life scenarios differ and other types of memory are more frequently used
            - remember faces/events
            - validity - mundane realism

- they were not testing the duration
      - the counting backwards cause the participants to displace the syllable rather than simply preventing rehearsal