Memory

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Capacity of STM - Jacobs 1887

Advantages

  • A strength of this study is that it was carried out in a very controlled way.It was a laboratory experiment and so the researcher had a high level of control over all variables. For instance, a possible extraneous variable would have been the pace of which the letters/digits were read out. It would of been unfair an unfair if they were read in a slow way to some pps but then in a fast way for others. To control this extraneous variable a metronome was used to ensure they were all read out at the same pace.
  • Another strength of this study is that the findings are reliable. We can say this because several researchers have found the same as Jacobs, that is, the capacity of STM is around seven items of information. For example, Miller 1956 wrote a very influential paper in which he argued for the 'magic number seven' - the capacity of memory being around 7 plus or minus 2 pieces of information.

Disadvantages

  • A limitation of this study is that it is low in ecological validity. Whilst the experimental method was good in that it gave the researcher a high degree of control it can also be criticised due to it's artificial nature. The argument goes that this experiment is not representative of the kinds of STM tasks we do in day to day life and so is of limited value in extending our knowledge of the capacity of STM.
  • A final limitation of this study is that it lacks temporal validity. This means that the findings may not generalise to modern times as it was carried out over 100 years ago. However, this criticism is likely to be unfounded as something like the capacity of the STM is unlikely to change over a relatively short period of time. Furthermore, recent research findings have consistently supported Jacobs findings demonstrating the reliability of these findings.

Evaluation

Conclusions: STM does have a limited capacity of somewhere between 5 and 9 items depending on the material used digits or letters and age.- Jacobs suggested that it may be easier to recall digits because there were only 9 digits but 25 letters. When you recall letter there are more options and so more chance of picking the wrong letter.- Capacity may increase with age due to increasing capacity , or due to the learning of techniques that keep information in memory.

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