Serial position phenomena: Training and retrieval effects

With successive free recall lists primacy items are usually among the first to be reported on the initial list. Recency items will then take over and be first reported on later lists. This retrieval shift was studied under varied list conditions designed to counteract ordinary position effects, and proved to be a stable and resistent effect. One experiment had subjects practice on five different free recall lists over three trials, and the results agreed with the hypothesis that primacy reduction is caused by proactive interference rather than by the primacy to recency report shift. Experiments of the usual one-session laboratory type have consistently failed to show practice effects on serial lists with incompatible spatial and temporal order cues. In a case study of five subjects examined over a period of three months only slight improvement on single-trial lists was observed. However, when naive subjects were given four successive trials with the same type of cue-conflict list, prominent practice effects were easily demonstrated. Observations confirmed the assumption that repeated presentations of items located in middle list positions may counteract the privilege of primacy and recency positions. When repetitions were made within contracting and expanding lists, the results proved that active anchoring, making itself visible as primacy effects, is feasible with contracting lists but difficult with expanding lists. Active performance of list learning strategies generally results in primacy effects; whereas passive shortcut procedures, in learning and retrieval of information, produce recency effects. Predominant recency effects are symptoms of difficult task situations only partially mastered by the learner; primacy effects point to more successful elaboration. Overall, serial position effects do not seem to be due to structural memory stores so much as to the working of cognitive strategy factors. A problem-solving theory was presented as an alternative to information-processing models of serial learning and memory.     

Recency judgments as a function of word frequency: A framing effect and frequency misattributions

The effects of word frequency on judgments of recency of item presentation were examined in two experiments. Subjects in Experiment 1 were presented two mixed lists of high- and low-frequency words followed by a list assignment task for recognized items. It was found that subjects were biased toward assigning low-frequency words to the more recently presented list. Subjects in Experiment 2 were presented a single mixed list of high- and low-frequency words followed by either a relative recency of presentation judgment task or a relative primacy of presentation judgment task. Each word pair on the tests contained one high-frequency word and one low-frequency word. It was found that, for the recency judgment task, subjects were biased to select the low-frequency item as having been presented more recently. However, on the parallel primacy judgment task, there were no effects of word frequency; moreover, overall accuracy levels were higher with primacy than with recency instructions. We interpret the effects of word frequency on recency judgments in Experiments 1 and 2 in terms of a misattribution of frequency-related differences in recollection-based recognition. The finding that recency and primacy instructions produced different patterns of results provides further evidence (Flexser & Bower, 1974) for an effect on performance of the way in which the temporal judgment task was framed.     

A recency-based account of the list length effect in free recall

Free recall was examined using the overt rehearsal methodology with lists of 10, 20, and 30 words. The standard list length effects were obtained: As list length increased, there was an increase in the number and a decrease in the proportion of words that were recalled. There were significant primacy and recency effects with all list lengths. However, when the data were replotted in terms of when the words were last rehearsed, recall was characterized by extended recency effects, and the data from the different list lengths were superimposed upon one another. These findings support a recency-based account of episodic memory. The list length effect reflects the facts that unrehearsed words are less recent with longer lists, and that with longer lists, a reduced proportion of primacy and middle items may be rehearsed to later positions.     

Auditory list memory and interference processes in monkeys.

Memory of 2 rhesus monkeys (Macaca mulatta) was tested in a serial probe recognition task with lists of 4 natural or environmental sounds, different retention intervals, and different manipulations of interference. At short retention intervals, increasing the separation of list items reduced the primacy effect and produced a recency effect. Similar results were shown by increasing interference across lists through item repetitions or making the first 2 list items high-interference items. These results indicated that decreasing first-item performance reduced proactive interference on memory of the last list items. At long (20 s) retention intervals, making the last list items of high interference reduced the recency effect, reduced retroactive interference, and produced a primacy effect. Taken together, interference plays a role in determining the primacy and recency effects of the serial-position function.     

Serial position effects in recall of television commercials

Does the position of a television commercial in a block of commercials determine how well it will be recalled? The findings of naturalistic studies can be affected by uncontrolled presentation, viewing, and retention variables. In the present article, college students viewed lists of 15 commercials in a laboratory simulation and recalled the product brand names. In an immediate test, the first commercials in a list were well recalled (a primacy effect), as were the last items (a recency effect), in comparison with the recall of middle items. In an end-of-session test, the primacy effect persisted, but the recency effect disappeared. Embedding lists within a television program again produced better recall of the first items during end-of-session tests of recall and recognition. These results offered convergent validity for the naturalistic studies of commercial memory, and they supported the usefulness of combining laboratory and field methods to answer questions about everyday memory.     

Temporal associations and prior-list intrusions in free recall

When asked to recall the words from a just-presented target list, subjects occasionally recall words that were not on the list. These intrusions either appeared on earlier lists (prior-list intrusions, or PLIs) or had not appeared over the course of the experiment (extra-list intrusions). The authors examined the factors that elicit PLIs in free recall. A reanalysis of earlier studies revealed that PLIs tend to come from semantic associates as well as from recently studied lists, with the rate of PLIs decreasing sharply with list recency. The authors report 3 new experiments in which some items in a given list also appeared on earlier lists. Although repetition enhanced recall of list items, subjects were significantly more likely to make PLIs following the recall of repeated items, suggesting that temporal associations formed in earlier lists can induce recall errors. The authors interpret this finding as evidence for the interacting roles of associative and contextual retrieval processes in recall. Although contextual information helps to focus recall on words in the target list, it does not form an impermeable boundary between current- and prior-list experiences.     

Serial position and clustering effects in a chimpanzee’s “flee recall”

Lana, a chimpanzee sophisticated in the language Yerkish, was tested for free recall on lists consisting of from one to eight words randomly drawn from one of three taxonomic categories or on lists consisting of nine words with every third word from a different category. Serial position effects were observed for the four- to eight-item lists, with statistically significant first-item primacy effects on the seven- and eight-word lists and last~position recency effects on the six-, seven-, and eight-word lists. Also, above-chance clustering was observed in the recall of the nine-item categorized lists. These results were compared and contrasted with the serial position and clustering effects obtained in free recall with humans. Several alternative theoretical accounts of the results were considered.     

Inter- and intra-individual variation in immediate free recall: an examination of serial position functions and recall initiation strategies

Serial position functions in immediate free recall have been historically noted for their bowed shape, where items presented at the beginning (primacy) and end (recency) of a list are better remembered than those presented in the middle. While extensive work has examined these effects, researchers typically ignore the systematic differences among individuals that likely contribute, but are lost when using an aggregate function. In the current study, inter- and intra-individual differences in serial position functions and differences in recall strategies were examined. Participants performed a free recall task on multiple lists. Three groups of participants were derived based on the relative profiles in their serial position functions. These groups differed in the extent that they output mainly primacy items, recency items, or both primacy and recency items. Performance on immediate free recall and on cognitive ability tasks was compared between these three groups. Systematic inter- and intra-individual variation in recall strategies led to differential profiles of performance in immediate free recall, which was also related to the additional cognitive ability measures. Performance on a task can be due to the utilisation of a variety of control processes that emphasise various components of that task over other components.     

词频、易接近性和词表序列成分对近因效应影响的实验研究

本研究目的探讨词频、易接近性和词表序列成分对近因效应的影响及其原因。两个实验以不同词频和不同易接近性的中文词为材料,运用直接自由回忆程序和操纵词表的组成成分,探讨近因效应的特点。实验结果表明：词频对近因效应的作用受词表序列成分的影响,对于纯的词表,高频词回忆的比例比低频词更高,对于混合词表,低频词回忆的比例比高频词更高,但是词的易接近性不影响近因效应且不受词表序列成分影响。文章最后对近因效应的性质进行了讨论。     

Predictability as a task demand in single-trial free recall

In a series of five single-trial free recall experiments it was demonstrated how manipulations of predictability in a list learning task caused reliable effects on the recency portions of the nominal serial position curve. Predictability was defined as knowledge of when the next item in the list should appear ( interval predictability) and knowledge of when the list should end and thus when recall could start ( signal predictability). Predictability was manipulated by varying the inter-item intervals within a list according to different "encoding functions", e.g. a successive increase (Condition I ) or decrease (Condition D ) of the inter-item intervals. Predictability was also manipulated by means of post-list recall signals. The data obtained show, that depending on how the interval and the signal predictabilities were manipulated, either Condition I or Condition D lists could be made more beneficial to the recall of recency items than lists with constant inter-item intervals (Condition C ). Previous encoding, storage and retrieval models were found not to give satisfactory accounts of the obtained recency effects. Neither could any traditional rehearsal model explain the data. Instead it is proposed that the predictability of stimuli in a list learning task explains how changes in recall of recency items come about. It was also hypothesized that the temporal demands, afforded to the subjects by the different encoding functions, explained the obtained output order variations.     

Auditory List Memory in Rhesus Monkeys

Auditory memory of 2 rhesus monkeys was tested in a serial probe recognition task. Lists of four environmental or natural sounds were followed by a retention interval and a test. The test matched one of the list items on half of the trials. The retention interval was varied across sessions. Six experiments showed similar results and changes in the serial position function. At short retention intervals, there was good memory for first list items (primacy effect) and poor memory for last list items. At intermediate retention intervals, memory improved for last list items (recency effect). At long retention intervals (20 s and 30 s), the recency effect was strong, and the primacy effect had dissipated. These auditory primacy and recency effects and their changes with retention interval were opposite to those for visual memory. Implications for processes and mechanisms of memory are discussed.     

Presence and absence of serial position effects in short-term memory

The nature of serial position effects was examined with a method based on pooled observations. With standard list presentation procedures, primacy and recency effects in short and long-term memory were observed. When learning operations were directed away from end positions, by changes in presentation rate, by within-list repetitions, by focusing instructions, and by differential grouping of list items, the usual serial position pattern was found to be affected in several ways, primacy and recency effects often being absent. Attempts to create anchor points and to ascribe serial positions verbally, were generally found to favour recency over primacy effects. Taken as a whole, the results, all of them based on recall of lits given a single presentation, indicated that position phenomena are more easily influenced by functional than by structural factors. The findings were explained in terms of a two-stage conception of serial learning, doing without specific storage assumptions.     

Visual list memory in capuchin monkeys (Cebus apella)

Memory of 3 capuchin monkeys, Cebus apella, was tested with lists of 4 travel-slide pictures and different retention intervals. They touched different areas of a video monitor to indicate whether a test picture was in a list. At short retention intervals (0 s, 1 s, 2 s), memory was good for the last list items (recency effect). At a 10-s retention interval, memory improved for 1st list items (primacy effect). At long retention intervals (20 s and 30 s), primacy effects were strong and recency effects had dissipated. The pattern of retention-interval changes was similar to rhesus monkeys, humans, and pigeons. The time course of recency dissipation was similar to rhesus monkeys. The capuchin's superior tool-use ability was discussed in relation to whether it reflects a superior general cognitive ability, such as memory. In terms of visual memory, capuchin monkeys were not shown to be superior to rhesus monkeys.     

Output order in immediate serial recall

In two experiments, we examined the effect of output order in immediate serial recall (ISR). In Experiment 1, three groups of participants saw lists of eight words and wrote down the words in the rows corresponding to their serial positions in an eight-row response grid. One group was precued to respond in forward order, a second group was precued to respond in any order, and a third group was postcued for response order. There were significant effects of output order, but not of cue type. Relative to the forward output order, the free output order led to enhanced recency and diminished primacy, with superior performance for words output early in recall. These results were replicated in Experiment 2 using six-item lists, which further suggests that output order plays an important role in the primacy effect in ISR and that the recency items are most highly accessible at recall.     

Memory for lists of spatial events in the rat

Three experiments are reported in which rats were presented with lists of spatial events or responses in distinct visual contexts, and retention subsequently was measured for the events occuring at each serial position. In Experiments 1 and 2, lists contained different numbers of forced choices on successively presented T-mazes, and memory for each serial position was tested on each trial. In Experiment 3, lists were made up of different numbers of forced entries into randomly ordered arms on the eight-arm radial maze, and memory for one serial position was probed on each trial. All three experiments yielded serial position curves which demonstrated recency effects but no primacy effects. Comparisons of retention for different list lengths within each experiment indicated that retention of shorter lists was equivalent to retention of the final items of longer lists and superior to retention of the initial items on longer lists. This pattern of results indicated that there was no evidence of proactive inhibition in the serial position curves. Analysis of input and output interference effects and the results of control tests suggested that both retroactive inhibition and time-based forgetting processes were responsible for recency effects.     

Immediate serial recall of mixed-modality lists

Seven experiments are reported in which subjects were tested for immediate serial recall of mixed-modality lists. On mixed auditory-visual lists, there was an advantage for auditory items at all serial positions. This was due to both a facilitation of auditory items and an inhibition of visual items on mixed lists, as compared with single-modality lists. When presented on a list containing items read silently, recall of items that were silently mouthed by the subject demonstrated patterns similar to those found with auditory items. When presented on a list containing items read aloud, recall of mouthed items showed patterns similar to those found with silently read items. The auditory advantage on mixed lists was found even when the list items were acoustically similar or identical and was not reduced by midlist auditory suffixes. The results suggest that modality differences in recall of mixed-modality lists are based on information different from that responsible for modality differences in recall of single-modality lists.     

Relation between intelligence and short-term memory

Several prior studies have concluded that the correlation between IQ and STM depends on differences in encoding or rehearsal strategies. Low IQ subjects use less effective strategies than high IQ subjects. One basis for these conclusions is that IQ exerts its greatest influence on the recall of early items in to-be-remembered lists, having little effect on the recall of recency items. The present study measured IQ/STM correlations in children, using probed serial recall of supraspan digit lists. The results showed the predictive power of IQ to range from a maximum in the case of recall for recency items to practically zero in the case of primacy items. Several explanations for the data are discussed, taking account of the possible roles of individual differences in rehearsal, in item persistence, and in the ability to access specified information in a short-term store.     

An experimental analysis of memory processing

Rhesus monkeys were trained and tested in visual and auditory list-memory tasks with sequences of four travel pictures or four natural/environmental sounds followed by single test items. Acquisitions of the visual list-memory task are presented. Visual recency (last item) memory diminished with retention delay, and primacy (first item) memory strengthened. Capuchin monkeys, pigeons, and humans showed similar visual-memory changes. Rhesus learned an auditory memory task and showed octave generalization for some lists of notes--tonal, but not atonal, musical passages. In contrast with visual list memory, auditory primacy memory diminished with delay and auditory recency memory strengthened. Manipulations of interitem intervals, list length, and item presentation frequency revealed proactive and retroactive inhibition among items of individual auditory lists. Repeating visual items from prior lists produced interference (on nonmatching tests) revealing how far back memory extended. The possibility of using the interference function to separate familiarity vs. recollective memory processing is discussed.     

Distinctiveness and Very Short-term Serial Position Effects

The serial position function reflects better memory for the first and last few items in a list than for the middle items. Four experiments examined the effects of temporal spacing on the serial position function for five-item lists that took between 0.5 seconds and 1.1 seconds to present. As with recall of far longer-lasting lists, recency and other robust serial position effects were observed with both free and serial recall. We demonstrate that temporal schedules of presentation control recall probability in predictable ways, and conclude that very fleeting lists obey similar principles as do longer-lasting lists. We compare both sets of findings with predictions from the dimensional distinctiveness framework.