Serial Position Function
The predictable patterns of memory and forgetting of lists of stimuli.
When a person attempts to recall a set of stimuli that exceeds about seven items, there is a high likelihood that he or she will forget some of them. The generally accepted limit to memory for material that is not rehearsed is referred to as "the magic number seven" (plus or minus two items). Most studies in this area have employed lists of words or nonsense syllables, but the research results hold true for a wide range of stimuli.
As a rule, if free recall is engaged, the words that are best remembered are those from the end of the list, and they are also likely to be the first to be recalled. This tendency for the best memory for recently presented items is referred to as the recency effect. (The tendency for retrieving words from the beginning of a list is called the primacy effect.) Recall will be poorest for items in the middle of the list, unless a stimulus has special characteristics and stands out.
When a learner must use serial recall, or recall of the stimuli in their order of presentation, the items appearing first and last on the list still show an advantage over those in the middle, but the items at the beginning of the list are recalled more often than items at the end of the list, a reversal of the pattern in free recall.
The serial position effect occurs due to three factors: distinctiveness, constraints of short-term memory, and inhibition. First, the primacy and recency effects occur because items at the beginning and the end of the list are distinct or isolated from the other stimuli due to their positions. Second, short-term memory involves keeping some information in active, working memory; this information is likely to be the most recently presented stimuli. Third, inhibition hampers memory. Words in a list tend to interfere with one another. When they are at the beginning or at the end of the list, they are not surrounded by as many words that could interfere with them; words in the middle, on the other hand, must compete for space in working memory with more words around them.
See also Free-recall learning.
Squire, Larry R. Memory and Brain. New York: Oxford University Press, 1989.