Some of the strongest evidence for themulti-store model(Atkinson & Shiffrin, 1968) comes from serial position effect studies and studies of brain-damaged patients.
The serial position effect is the tendency to remember the first and last items in a series better than those in the middle. It is a form of cognitive bias that is thought to be due to how information is processed and stored in memory.
The tendency to recall earlier words is called the primacy effect; the tendency to recall later words is called the recency effect.
Murdock (1962)
Procedure
Murdock presented participants with lists of 10 to 40 words, one word at a time, at a rate of either one word per second or one word every two seconds.
The participants were assigned to one of the six groups, each of which had a different combination of list length and presentation rate.
After the list was finished, participants were asked to recall as many words as they could in any order.
Results
Murdock found that the probability of recalling any word depended on its serial position in the list.
Words presented early in the list (primacy effect) and at the end of the list (recency effect) were more often recalled, while words in the middle were more frequently forgotten.
The recency effect extended over the last 8 serial positions and was present even in longer lists of up to 40 words.
Additionally, Murdock observed a flat middle section (asymptote) in the serial position curve, which was less pronounced in shorter lists.
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.
Conclusion
Separate Memory Stores
According to themulti-store model, when participants recall words from the beginning and end of the list, they are retrieving information from two separate memory stores: long-term memory for the primary information and short-term memory for the recent information.
The primacy effect occurs because participants have time to rehearse the first few words in the list, transferring them from short-term memory tolong-term memory.
The recency effect occurs because the last few words in the list are still available inshort-term memory, which is thought to have a capacity of around 7 items.
Inhibition Effects
Murdock suggested that the shape of the serial position curve might be a result of proactive and retroactive inhibition effects occurring within the list itself.
He noted that the primacy effect levels off after the first 3 or 4 serial positions, consistent with findings that proactive interference effects in short-term memory are greatest after about 3 prior words.
The horizontal asymptote in the middle of the list agrees with the observation that retroactive interference effects in short-term memory approach a non-zero asymptote.
Lastly, the S-shaped recency effect aligns with the curve of retroactive interference in short-term memory. Murdock proposed that these inhibition effects combine to produce the characteristic shape of the serial position curve in free recall.
Strengths
Weaknesses
Glanzer and Cunitz (1966)
The study involved two separate experiments (immediate vs delayed recall).
Participants were Army enlisted men (not randomly assigned). They recalled 20-word lists in Exp I and 15-word lists in Exp II.
Experiment I (Immediate Recall)
In Experiment I, presentation rate (1S/P, 2S, 3S) and repetition of words (1S/P, 2P, 3P) were manipulated to examine effects on long-term storage and the beginning of the serial position curve.
Experiment II (Delayed Condition)
In Experiment II, delay between end of list and recall (0, 10, 30 sec) was varied to examine effects on short-term storage and the end of the serial position curve. During the delay, subjects counted out loud.
Primacy Effect (Experiment I)
Recency Effect (Experiment II)
References
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.
Olivia Guy-Evans, MSc
BSc (Hons) Psychology, MSc Psychology of Education
Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.
Saul McLeod, PhD
BSc (Hons) Psychology, MRes, PhD, University of Manchester
Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.
