Procedures: Participants were presented with sets of trigrams (nonsense syllables in sets of three, eg. BCM) which they were then asked to recall in order after a delay of 3, 6, 9, 12, 15 and 18 seconds.

The INDEPENDANT VARIABLE was the time delay.

The DEPENDANT VARIABLE was the number of trigrams recalled.

Participants were given an interferance task of counting backwards in threes from a random threee digit number to prevent rehearsal (known as the Brown-Peterson technique).

Recall had to be 100% accurate and in the correct order in order for it to count as correctly recalled.

Findings: The percentage recall was:

After 3 SECONDS = 80%
After 6 SECONDS = 50%
After 18 SECONDS = LESS THAN 10%

Recall decreases steadily between 3 and 18 seconds suggesting that the duration of the STM is not much more than 18 seconds.

Evaluation: This study lacks MUNDANE REALISM as the recall of trigrams is not likely to occur in everyday situations, therefore the results cannot be generalised.

The trigrams are NOT MEANINGFUL, evidence from other studies suggests that meaningful information is more likely to be recalled.

The case study of "HM" contradicts these findings as he could only successfully use his STM (as his LTM was damaged) yet he could recall new memories for up to 15 MINUTES before they decayed.

The experiment was strictly controlled, therefore CAUSE CAN BE SEPARATED FROM EFFECT. Therefore it can be said that time delay DOES CAUSE recall to decline.