Some of the strongest evidence for the multi-store model (Atkinson & Shiffrin, 1968) comes from serial position effect studies and studies of brain-damaged patients.
Experiments show that when participants are presented with a list of words, they tend to remember the first few and last few words and are more likely to forget those in the middle of the list.
This is known as the serial position effect. The tendency to recall earlier words is called the primacy effect; the tendency to recall later words is called the recency effect.
Murdock asked participants to learn a list of words ranging in length from 10 to 40 words and free recall them. Each word was presented for one to two seconds.
He found that the probability of recalling any word depended on its position in the list (its serial position).
Words presented either early in the list or at the end were more often recalled, but the ones in the middle were more often forgotten. This is known as serial position effect.
The improved recall of words at the beginning of the list is called the primacy effect; that at the end of the list, the recency effect. This recency effect exists even when the list is lengthened to 40 words.
Murdock suggested that words early in the list were put into long term memory (primacy effect) because the person has time to rehearse each word acoustically.
Words from the end of the list went into short term memory (recency effect) which can typically hold about 7 items.
Words in the middle of the list had been there too long to be held in short term memory (STM) (due to displacement) and not long enough to be put into long term memory (LTM). This is referred as a asymptote.
In a nutshell, when participants remember primary and recent information, it is thought that they are recalling information from two separate stores (STM and LTM).
Glanzer and Cunitz (1966)
Glanzer and Cunitz presented two groups of participants with the same list of words.
One group recalled the words immediately after presentation, while the other group recalled the words after waiting 30 seconds.
These participants had to count backwards in threes (the Brown-Peterson technique), which prevented rehearsal and caused the recency effect to disappear. Both groups could free recall the words in any order.
The words at the end of the list are only remembered if recalled first and tested immediately. Delaying recall by 30 seconds prevented the recency effect.
Atkinson, R. C., & Shiffrin, R. M. (1968). Chapter: Human memory: A proposed system and its control processes. In Spence, K. W., & Spence, J. T. The psychology of learning and motivation (Volume 2). New York: Academic Press. pp. 89–195.
Glanzer, M., & Cunitz, A. R. (1966). Two storage mechanisms in free recall. Journal of Verbal Learning and Verbal behavior, 5(4), 351-360.
Murdock, B. B. (1962). The serial position effect of free recall. Journal of Experimental Psychology, 64(5), 482–488.