Peterson and Peterson 1959 duration of stm

Aim: To investigate the duration of STM

Method:Participants were presented with sets of nonsense trigrams. They were asked to recall them either after 3, 5, 8 ,11 ,15 or 18 seconds. During this pause participants were presented with an interference task - used to prevent rehersal of the trigrams. 

Results: The results showed that after 3 seconds, 80% of participants were able to recall. However after 18 seconds, only 10% could be recalled accurately.

Conclusion: When rehersal is prevented, very little information can be stored in stm for longer than 18 seconds.

Evaluation: The experiment was artificla and lack ecological validity. If the information presented had been more semantic, stm could have shown to have an even greater capacity. Only one type of stimulus was used. the duration of stm may depend on the type of stimulus used. Also, ppts were presented with several trigrams. This may have confused some, meaning that only the first trigram was realistically trialled. 

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  • Created by: FelixShaw
  • Created on: 23-09-13 19:22

Jacobs 1887 Capacity of stm

Method: Participants presnted with a string of either letters or digits. they were then asked to repat the strings exactly. The no. of letter and digits in each string increased until the sequence failed to be recalled correctly.

Results: The majority of the time, ppts were only able to recall 9 digits and 7 letters. However this increased with age in childhood.

Conclusion: Jacobs' results suggested that stm has a limited storage capacity and can only hold up to betwen 5-9 items at a time. (Millers law). Individual differences were found, such as stm increasing with age. This could have been due to larger brain capacitty, or through the use of memory techniques thoughout adolecene development, such as chunking. Also, there were only a max of 10 digits in a sequence, where as there was a max of 26 letters.

Evalution: Jacobs research is artificial and lacks ecological validity. If the information presented to ppts had been more semantic, perhaps stm would have been shows to have an ever greater capacity. Also, previous sequences would have confused ppts for future sequences.

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