Free recall

Free recall is a basic paradigm in the psychological study of memory. In this paradigm, participants study a list of items on each trial, and then are prompted to recall the items in any order (hence the name "free" recall). Items are usually presented one at a time for a short duration, and can be any of a number of nameable materials, although traditionally, words from a larger set are chosen. The recall period typically lasts a few minutes, and can involve spoken or written recall. The standard paradigm involves the recall period starting immediately after the final list item; this can be referred to as immediate free recall (IFR) to distinguish it from delayed free recall (DFR). In delayed free recall, a short distraction period is interpolated between the final list item and the start of the recall period. Both immediate free recall and delayed free recall have been used to test certain effects that appear during recall tests, such as the primacy effect and recency effect.

One of the basic measures of performance in the free recall paradigm is simply the number of words recalled from a list, which varies with a number of factors, including the list length, the type of material studied, and any task used to process the words (e.g., a simple judgement). When one examines the probability of recall by the position of the item in the list (its serial position), one finds that the initial and terminal items in the list are better remembered than those in the middle (also known as the primacy and recency items, respectively). Primacy effects generally come from the idea that greater attention is devoted to items that appear at the beginning of presentation lists. Murdock presents a classic study of serial position effects in free recall. In his experiment, Murdock used six groups of 103 participants. Each group was given different combinations of list lengths and presentation rates. Three of the groups were shown lists of ten, fifteen, and twenty words with a presentation rate of two seconds per word. The other three groups were shown lists of twenty, thirty, and forty words with a one-second presentation rate for each word. There were 80 lists in total that included randomly selected common English words. After the presentation of each list, subjects were asked to recall as many words as possible in any order. Results from the experiment showed that all groups expressed both primacy effects and recency effects. Recency effects were exhibited regardless of the length of the list, and it was strongest for the words in the last eight serial positions. The primacy effect extended over the first four serial positions.

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