Research on Duration

What are the two main areas of research on duration?

• Duration of STM

• Duration LTM

Describe Margaret and Lloyd Peterson’s (1959) investigation on Duration of STM?

• Duration is the defining feature of STM

• They tested 24 undergraduate students

• Each students took part in 8 trials

• On each trial, they were given a consonant syllable (known as trigram eg: YCG) to remember and a 3 digit number

• The student was then ask to count backwards from the 3 digit number until told to stop.

• This was to prevent mental rehearsal of the consonant syllable

• One each trial they were told to stop after a different amount of time: 3, 6, 9, 12 15, 18 seconds. This is called retention interval.

• The percentage of trigrams correct decreased when interval length increased.

• It suggests STM duration may be very short, unless verbal rehearsal is used.

What are limitations of the Peterson study?

• The stimulus material was artificial. Trying to memorise consonant syllables doesn’t reflect reality.

• It lacks external validity.

• Can be used in life eg, phone numbers

Describe Harry Bahrick et al (1975) study on the Duration of LTM:

• They studied 392 participants from Ohio between the age 17 & 74.

• High school yearbooks were obtained and recall was tested in various ways.

• One test was a photo recognition test of 50 photos

• The second test was free recall where participants reccalled all the names of their graduating class without photos.

What were the results of their study?

• Within 15 years of graduation, 90% success rate, after 48 years it declined to 70% photo recognition.

• Free recall was less, with 60% accuracy after 15 years and 30% after 48 years.

Give an evaluation of Harry Bahrick’s study:

• It has high external validity

• Real life meaningful memories were studied.

• When studies n LTM have been conducted with meaningless pictures, recall rates were lower.

• Confounding variables weren’t controlled, could have rehearsed names.