He tested 24 undergraduate students.

-Each trial ppts were given a consonant syllable (trigram, e.g. YCG) to remember and a 3 digit number.

-Ppts were asked to count backwards from the 3 digit number until they were told to stop and then they had to try and recall the trigram. The counting backwards was to try and prevent the ppts from rehearsing the trigram.

-In each trial they were asked to count back for different amounts of time – 3, 6, 9, 12, 15, or 18 seconds = called the retention interval.

-STM has a very short duration – 18-30 seconds - if information is not repeated or rehearsed.