Multitrial free and serial recall tasks differ both in recall instruction and in presentation order across trials. Waugh (1961) compared these paradigms with an intermediate condition: free recall with constant presentation order. She concluded that differences between free and serial recall were due only to recall instructions, and not to presentation order. The present study reevaluated the relation between free and serial recall, using Waugh's three conditions. By examining recall transitions and the organization of information retained across trials, we conclude that presentation order is an important factor, causing participants to exhibit the same temporal associations in serial recall and in free recall with constant presentation order.

Older adults show poorer performance than young adults at word list recall, especially for order information. In contrast with this temporal association deficit, older adults are generally adept at using preexisting semantic associations, when present, to aid recall. We compared the use of temporal and semantic associations in young and older adults' word list recall following both free recall and serial recall instructions. Decomposition of serial position curves confirmed that older adults showed weakened use of temporal context in recall in relation to young adults, a difference that was amplified in serial recall. Older adults' temporal associations were also less effective than young adults' when correlated with serial recall performance. The differential age decrement for serial versus free recall was accompanied by a persistent influence of latent semantic associations in the older adults, even when maladaptive for serial recall.

To test the hypothesis that serial recall depends largely on the encoding and retrieval of position-toitem associations, we examined whether people can learn "spin" lists on which starting position is randomly varied across successive learning trials. By turning positional information from a reliable cue into a source of inter-trial interference, we expected learning to be greatly impaired. Contrary to this hypothesis, we found that participants were only slightly worse at serial learning under spin conditions and that this impairment reflects a substantial increase in initiation errors coupled with a small increase in inter-trial forgetting. These data show that participants can effectively use nonpositional cues when positional cues are unreliable.Keywords serial learning; serial-order memory; serial recall Ebbinghaus inaugurated the laboratory study of human memory through his experiments on serial learning-the ability to reproduce a sequence of unrelated items in their order of presentation through successive study and test trials. The theoretical question that has puzzled memory scholars for more than a century since his pioneering work concerns the nature of the stored information that supports this capacity. Historically, the classic theory of serial learning was associative chaining. Chaining theory states that each item in a list is linked most strongly to its immediate neighbors (Ebbinghaus, 1885(Ebbinghaus, /1913Robinson, 1932). As noted by Ebbinghaus (1885Ebbinghaus ( /1913, "…the associative threads, which hold together a remembered series, are spun not merely between each member and its immediate successor, but beyond intervening members to every member which stands to it in any close temporal relation" (p. 94). Retrieval of the first list item facilitates retrieval of the second, and the second facilitates retrieval of the third, and so forth. By somehow accessing the first (or last) item, one can chain forward (or backward) through the sequence. Ladd and Woodworth (1911) noted that people are not limited to just using sequential relations among items to reproduce a sequence. On the basis of the strategies reported by their participants, they suggested that at least some people are able to represent positional information about the studied items, and to use that positional information to facilitate recall. As summarized by Woodworth (1938), "…Grouping, whether rhythmical or spatial, provides a blank form into which the items are inserted. …Remembering the list consists largely in Correspondence concerning this article should be addressed to Michael J. Kahana, 3401 Walnut St., Suite 303C, Philadelphia, PA 19103, USA; kahana@psych.upenn.edu; fax: 215-746-6848. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript finding the items in their places" (p. 32). According to positional-coding hypothesis, as it came to be known, people associate each list item with a representation of the item's position in the input sequence. The first item is linked ...

Ever since Ebbinghaus (1885Ebbinghaus ( /1913, students of memory have sought to understand human sequence learning. Whereas early work analyzed the acquisition of long lists of items through repeated study and test trials (see Harcum, 1975, for a review), more recent studies have favored the analysis of immediate recall of relatively short lists (Brown, Preece, & Hulme, 2000;Burgess & Hitch, 1999;Cowan, Saults, Elliott, & Moreno, 2002;Farrell & Lewandowsky, 2002;Henson, 1998;Knoedler, Hellwig, & Neath, 1999;Li, Schweickert, & Gandour, 2000). This shift in attention reflects a desire to move to a finer grain of analyses-from measures of overall recall and learning to the analysis of the distribution of errors across individual list positions. This article bridges these two approaches by bringing a more detailed approach to the analysis of serial learning. Through analyses of both item and order gains and losses over trials, we show that one can distinguish among hypotheses of serial learning that are indistinguishable with analyses of mean recall accuracy alone.The effect of repetition on learning is most often measured by plotting a learning curve. Consider the free recall task, in which participants are asked to recall a justpresented list in any order. In this task, recall probability increases logarithmically with the number of study trials (Tulving, 1962). The logarithmic form of the learning curve could arise from different underlying processes. For example, participants might maintain the items they have already recalled, but pick up fewer and fewer new items over trials. Alternatively, participants might pick up new items at a constant rate, while forgetting a percentage of the items that they had previously recalled. This would lead to a higher absolute number of items being forgotten over trials, such that the net gain of recalled items still increases over trials. Looking solely at the learning curve, one cannot distinguish between these possibilities. But by examining what happens to individual items from trial to trial, one can test these hypotheses.In a classic analysis of the learning curve in free recall, Tulving (1964) examined these trial-to-trial transitions of individual items. He reminded us of two important features of episodic list-learning experiments. First, in most studies, which use words as stimuli, participants are not learning items per se; rather, they are learning that these items, mini-events in the experiment, occurred in a particular spatiotemporal context defining the study list. Tulving (1964) also noted that if queried immediately following an item's appearance on the list, participants would not have difficulty recalling that item. Thus, the process of learning is inextricably tied to the process of forgetting (and vice versa;Krueger, 1929). Tulving (1964) decomposed the learning curve into four mutually exclusive types of information. Consider the fate of a study item on a given learning trial. In one case, an item that was not recalled on the previous trial is recalled on...

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