Human Memory
Lesson 6
Human Memory Factors Affecting Duration in STM Produced by
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Factors Affecting Duration in STM Rehearsal: • The key point about the findings based on BrownPeterson technique is that items disappear from STM only when rehearsal is prevented. • New items can only take their place either if existing items move onto LTM or because they are forgotten. If we want to remember something for a short period, we tend to repeat it to ourselves.
For example: • When we look for a number in the phone book and need to hold it in our memory for long enough to dial it accurately. This repetition serves as a method of continually reinserting the information into STM and thereby strengthening the memory. Without rehearsal, the duration of STM is very brief.
Deliberate intention to recall: • Sebrechts et al. (1989) – briefly presented participants with lists of three common English nouns and then gave them an unexpected, serial recall test. • Correct recall of the items fell to 1% after only 4 seconds. • Studies such as these demonstrate that information can vanish from STM in a matter of a few seconds if people are not making a conscious effort to retain information.
Amount of information to be retained: • Murdock (1961) – presented participants with either a single three-letter word such as cat or three unrelated words such as hat, pen lid. • He then followed the same procedure as Brown and Peterson technique. • The forgetting curves for the three unrelated words were the same as for the consonant trigrams in Peterson and Peterson study.
• However, the single three letter word (which would be processed as one chunk) was resistant to forgetting and recall level was accurate still at 90% after 18 seconds. • This shows that, as in Miller’s digit span, the important factor is the number of chunks to be remembered rather than the number of individual items, i.e. letter.