Miller (1956)

• Miller studied the capacity of STM in his famous magic 7 experiment.
• Aim

  To discover the capacity of the STM.
• Procedure

  Using the digit span technique Miller asked participants to repeat digits IMMEDIATELY after him. Their score was calculated by the number of digits they could correctly recall.

  E.g.

  9

  08

  196

  2073

  31849

  684021

  1945021
• Findings

  Miller discovered that most participants could only recall between 5-9 items, in mathematics this is presented as 7 ± 2; ± meaning + (plus) or - (minus)
• Conclusion

  The capacity of the STM is limited to between 5-9 items, but it can be increased by chunking.
• Chunking


  putting long strings of information that can be difficult to remember into shorter more manageable chunks - like remembering phone numbers
• Evaluation of Miller

  ☺ Miller’s (1956) use of standardised digit span tasks (and similar series of discrete items) allowed him to tightly control extraneous variables such as presentation rate and item order. This rigour in design ensured that variations in recall were more likely due to intrinsic memory limits rather than external distractions, thereby reinforcing the reliability of the finding that STM can hold about 7 ± 2 items.
• Evaluation of Miller

  The very nature of the digit span task might have alerted participants to the memory challenge, prompting them to use specific mnemonic strategies (e.g., rehearsal or chunking) that they might not naturally employ in everyday memory tasks. This awareness could have artificially enhanced their performance, thereby questioning whether the observed capacity limit fully reflects natural STM functioning.