Duration Studies

__Peterson and Peterson (1959)__ wanted to test the theory that information is quickly lost from short-term memory if its not rehearsed.

__Bahrick et al. (1975)__ studied very long-term memory (VLTM) by testing the ability of people to recall the names of ex-classmates.

__Bahrick et al. (1975)__ studied very long-term memory (VLTM) by testing the ability of people to recall the names of ex-classmates.

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Peterson and Peterson (1959)

Peterson and Peterson (1959) wanted to test the theory that information is quickly lost from short-term memory if its not rehearsed.

Laboratory experiment.
24 psychology students participated.
Participants had to try and recall random trigrams (three consecutive consonants like GPR) after different intervals of time (3, 6, 9, 12, 15 and 18 seconds).
During these intervals, participants had to count backwards from a random number in groups of three and four. This was to stop them from rehearsing the trigrams in their heads.

Participants could recall fewer trigrams as the time gap increased.
- 3-second interval - participants recalled 80% correctly.
- 6-second interval - participants recalled 50% correctly.
- 18-second interval - participants recalled 10% correctly.

Our short-term memory has a limited duration when we can't rehearse information.
It's thought that decay (the automatic fading of memory that's not rehearsed) causes information loss from short-term memory.

Pros:
- Good control of variables - because of the laboratory setting.
Cons:
- Low ecological validity - because of the artificial set-up.
- Lacking variety of stimulus - no data on whether the type of stimulus affects the duration of the short-term memory.

Bahrick et al. (1975) studied very long-term memory (VLTM) by testing the ability of people to recall the names of ex-classmates.

The researchers set up a series of three tests to test the long-term memory of 392 participants.
The participants were tested 15 years, 30 years, and 48 years after graduation.

Free recall:
- Participants were asked to simply list the names of ex-classmates.
- They were given no prompts or materials to help them.
Photo-recognition:
- The participants were asked to recall the names of people from their photographs from their class yearbook.
- No list of names was given.
Name-recognition:
- The participants were asked to match the names of people to their photograph (i.e. they were given a randomised list of names).

The results showed that free recall (no pictures or memory cues) declined the most within 30 years, whereas name-recognition maintained a higher accuracy.
15 years after graduation:
- There was 90% accuracy for the name-recognition test.
- 60% accuracy for the free recall test.
- This was true even for large class sizes.

30 years after graduation:
- There was only 30% accuracy for free recall.
48 years after graduation:
- Name-recognition was 80% accurate.
- Photo-recognition was 40% accurate.

Bahrick et al. (1975) studied very long-term memory (VLTM) by testing the ability of people to recall the names of ex-classmates.

Overall, through the years recognition was more accurate than recall.
They concluded that the information is stored in the long-term memory but the information may be difficult to retrieve.

The forgetting process is very slow (compared to other studies which only examined memory in a laboratory setting).
Bahrick et al. attribute the slowness of forgetting to practice and the effect of overlearning.

People during high school spent a lot of time learning other peoples’ names and practising them.
- In other words, names that are well practised are difficult to forget.
This information (the names) is meaningful to the participants. Perhaps more so than, for example, other knowledge learnt during the same time period.

A main strength of the study was the high ecological validity.
It was a field experiment conducted over a long period of time and tested name recall.
Name recall is a skill that the majority of people use every day.

But because name recall is generally more meaningful to people, the results cannot be generalised to other types of information that people may hold in their long-term memory.
- E.g. childhood experiences, learned skills, etc.

The nature of the study made it very challenging to control for extraneous variables.
The study took place over approximately 50 years and so a lot of extraneous variables could have skewed the results.
- E.g. the researchers could not control how much contact the participants had with each other.
- It could be that some of them were in regular contact, increasing the amount of practice and so increasing the rate of recall.