Serial position effects in recognition memory for odors

Five experiments examined recognition memory for sequentially presented odors. Participants were presented with a sequence of odors and then had to identify an odor from the list in a test probe containing 2 odors. All experiments demonstrated enhanced recognition of odors presented at the start and end of a series, compared with those presented in the middle of the series when a 3-s retention interval between list termination and test was used. In Experiments 2 and 3, when a 30-s or 60-s retention interval was used, participants performed at slightly lower levels, although the serial position function was similar to that obtained with the 3-s retention interval. These results were noted with a 5-item (Experiments 1 and 4), 7-item (Experiment 2), 6-item (Experiment 3), and 4-item (Experiment 5) list of odors. As the number of test trials increased, recognition performance decreased, indicating a strong role for olfactory fatigue or interference in these procedures. A verbal suppression task, used in Experiments 4 and 5, had little influence on serial-position-based performance.     

Offloading memory: Serial position effects

Psychonomic Bulletin & Review - Despite the long history and pervasiveness of cognitive offloading as a memory strategy, the memorial fate of offloaded information is not well understood....     

Serial position effects in implicit memory

Serial position effects in explicit and implicit memory were investigated in a noncolour word Stroop task. Participants were presented with a study list of four words printed in different colours and were tested for memory of the list position of the colour (explicit memory task); they were then asked to complete a word stem primed (or not primed) by one of the words in the study list (implicit memory task), a task presented as a distractor task. Serial position effects were observed in both explicit and implicit memory, for both response times and proportion of correct responses, with marked primacy effects, a drop in performance towards the third list position and a rise in memory performance at the fourth list position, the recency effect being most pronounced in implicit memory. It is concluded that explicit and implicit expressions of memory are governed by similar principles of temporal information processing.     

Serial position effects in high-speed memory search

Ss decided whether or not a test digit had occurred in a previously presented memory set. Decision time increased with the size of the memory set at equal linear rates for positive and negative responses. Positive decision times were sensitive to the serial position of the test digit. Together, these results are incompatible with serial-exhaustive models; some modifications are necessary in order to accommodate the obtained results.     

Serial position effects in implicit memory for multiple-digit numbers

Serial position effects in implicit and explicit memory were investigated in a short-term memory task. A study list composed of four, spatially distributed, two-digit numbers was presented, followed by an item recognition task (explicit test) and an implicit memory task in which participants were asked to verify a simple addition equation where the presented answer was either primed or not primed by one of the number pairs in the study list. Similar serial position effects were observed in explicit and implicit memory, with faster response times for correct decisions on the first than on the later list positions. The presence of a primacy effect but no recency effect is consistent with previous studies of explicit memory with visual presentation. The results suggest that similar principles of temporal information processing govern priming and episodic short-term memory.     

Very short term recognition memory for odors

An investigation of very short term olfactory recognition memory was made with odors of low familiarity to subjects. The experimental procedure was that currently used to make qualitative similarity judgments on odors delivered in paired succession. Subjects made similarity judgments in a yes/no recognition paradigm on odors that were either identical or different. The dependence of recognition performance upon the degree of qualitative similarity was assessed by using two sets of dissimilar odor pairs: slightly dissimilar pairs (S1) and very dissimilar pairs (S2). Performance in terms of correct judgments (hits, correct rejections) was rather good for identical pairs in both sets and was nearly perfect for very dissimilar pairs with a delay of 2–300 sec, suggesting no effect of time or similarity on performance. However, for slightly dissimilar pairs, false alarms increased in number, thereby indicating a dependence of the recognition score on the qualitative distance between odors. In addition, false alarms tended to increase with the lengthening of the retention interval. It was suggested that the subjects based their responses on their capability to detect differences between odors rather than recognizing their similarities. Correct identifications were thus preserved at the cost of increasing false alarms when the discrimination task was made more difficult by closer similarity between odors (S1) or by the fading of memory traces with time. Studying the congruence between the similarity judgments and the kind of evocations associated with paired odors gives some support to the view that recognition performances had some cognitive/semantic basis.     

Serial position curves in spatial memory of rats: Primacy and recency effects

Memory for lists of items was tested in rats (N = 18) in an 8-arm radial maze. In Experiment 1 trials consisted of a study phase, in which the rat could freely choose five arms to obtain a food reward, and a test phase in which the animal was presented with a choice between a novel and a previously visited arm. The rat received additional food reinforcement only when visiting the novel arm. The two phases of a trial were separated by a retention interval of 30 sec or of 4, 16 or 60 min. It was found that recall of the five free arm choices was related to the serial position of the previously visited arm. There was a significant recency effect at the 30-sec delay. With longer retention intervals this disappeared, and a significant primacy effect could be observed. In Experiment 2 the same animals were given forced arm entries during the study phase and delays of 30 sec or 4 or 16 min before the test phase. Again, there was a trend towards a recency effect after the shorter delays and a significant primacy effect after the 16-min interval. These results show that, in the recall of lists of spatial items, rats have serial position curves with primacy and recency effects, depending on the length of the retention interval.     

Serial position effects in visual short-term memory for words and abstract spatial patterns

Two experiments tested the effects of list postion, and retention-interval in recognition for two distinct stimulus categories in young adults. Stimulus categories were spatial abstract patterns and words presented on a computer screen. At short delay intervals recency effects predominates and at longer delay intervals a primacy effect predominates in both experiments, indicating similar basic memory processes producing the serial position functions for the two different categories of visual stimuli, but as length of retention-interval increases, memory for first list items improves for words and remains constant for abstract patterns. Recency functions are similar for both stimulus categories tested.     

Serial position effects in semantic memory: reconstructing the order of verses of hymns

Serial position effects (primacy and recency) have been consistently demonstrated in both short- and long-term episodic memory tasks. The search for corresponding effects in semantic memory tasks (e.g., reconstructing the order of U.S. presidents) has been confounded by factors such as differential exposure to stimuli. In the present study, the stimuli were six-verse hymns that would have been sung from the first to the last verse by churchgoers on numerous occasions. Participants were presented with the verses of each hymn in random order and were required to reconstruct the correct order. Primacy and recency effects were significantly more evident for churchgoers than for nonchurchgoers. Moreover, error gradients were steeper than chance for churchgoers but not for nonchurchgoers; in other words, churchgoers' errors were more likely to be close to the correct position than further away. These findings provide the first unequivocal demonstration of serial position effects in semantic memory.     

Serial position functions for recognition of olfactory stimuli

Two experiments examined item recognition memory for sequentially presented odours. Following a sequence of six odours participants were immediately presented with a series of two-alternative forced-choice (2AFC) test odours. The test pairs were presented in either the same order as learning or the reverse order of learning. Method of testing was either blocked (Experiment 1) or mixed (Experiment 2). Both experiments demonstrated extended recency, with an absence of primacy, for the reverse testing procedure. In contrast, the forward testing procedure revealed a null effect of serial position. The finding of extended recency is inconsistent with the single-item recency predicted by the two-component duplex theory (Phillips & Christie, 1977 Phillips, W. A. and Christie, D. F. M. 1977. Components of visual memory. Quarterly Journal of Experimental Psychology, 29: 117–133. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). We offer an alternative account of the data in which recognition accuracy is better accommodated by the cumulative number of items presented between item learning and item test.     

Serial position functions for recognition of olfactory stimuli

Two experiments examined item recognition memory for sequentially presented odours. Following a sequence of six odours participants were immediately presented with a series of two-alternative forced-choice (2AFC) test odours. The test pairs were presented in either the same order as learning or the reverse order of learning. Method of testing was either blocked (Experiment 1) or mixed (Experiment 2). Both experiments demonstrated extended recency, with an absence of primacy, for the reverse testing procedure. In contrast, the forward testing procedure revealed a null effect of serial position. The finding of extended recency is inconsistent with the single-item recency predicted by the two-component duplex theory (Phillips & Christie, 1977). We offer an alternative account of the data in which recognition accuracy is better accommodated by the cumulative number of items presented between item learning and item test.     

Serial position effects for tonal stimuli

Serial position effects for tones were studied in a recognition memory experiment The S was given a stimulus list consisting of several tone bursts followed by a number of test tones. Accuracy of recognition of stimulus items as a function of input position followed the classical bowed serial position curve. Memory strength was a monotonically decreasing function of position in the test list. The data were fitted with a strength theory model of memory. The fit yielded decay parameters corresponding to stimulus- and response-induced interference, which were comparable to the parameters reported for meaningful verbal material.     

A reexamination of stimulus-frequency effects in recognition: two mirrors for low- and high-frequency pseudowords

The word-frequency mirror effect (more hits and fewer false alarms for low-frequency than for high-frequency words) has intrigued memory researchers, and multiple accounts have been offered to explain the result. In this study, participants were differentially familiarized to various pseudowords in a familiarization phase that spanned multiple weeks. Recognition tests given during the first week of familiarization replicated a result of W. T. Maddox and W. K. Estes (1997) that failed to show the classic word-frequency mirror effect for pseudowords; however, recognition tests given toward the end of training showed the classic mirror pattern. In addition, a stimulus-frequency mirror effect for "remember" vs. "know" judgments was obtained. These data are consistent with an account of the mirror effect that posits the involvement of dual processes for episodic recognition.     

Serial position curves in short-term memory: functional equivalence across modalities

Four experiments investigated item and order memory for sequences of seen unfamiliar faces and heard nonwords. Experiments 1 and 3 found bowed serial position curves using the serial reconstruction test of order with faces and nonwords, respectively. Experiments 2 and 4 found limited recency, no primacy, and above chance performance on all items using a two-alternative forced choice (2AFC) test of item recognition, again with faces and nonwords. These results suggest that the different serial position curves typically found using traditional paradigms for exploring visual and verbal short-term memory are due to differences in the methods used rather than modality-specific mechanisms.     

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.     

Serial position effects in 2-alternative forced choice recognition: Functional equivalence across visual and auditory modalities

Two experiments examined Ward, Avons, and Melling's (2005) proposition that the serial position function is task, rather than modality, dependent. Specifically, they proposed that for backward testing the 2-alternative forced-choice (2AFC) recognition paradigm is characterised by single-item recency irrespective of the modality of the stimulus presentation. In Experiment 1 the same nonword sequences, presented both visually or auditorily, produced qualitatively equivalent serial position functions with 2AFC testing. Forward testing produced a flat serial position function, while backward testing produced two-item recency in the absence of primacy. In order to rule out the possibility that the serial position functions for visual stimuli were the product of sub-vocal rehearsal, Experiment 2 employed articulatory suppression during the presentation phase. Serial position function equivalence was again observed together with a modest impairment in overall recognition rates. Taken together, these data are consistent with the Ward et al. proposition and further support the existence of a visual memory that can facilitate storage of visual-verbal material (e.g. Logie, Della Sella, Wynn, & Baddeley, 2000). However, the observation of two-item recency contradicts the original duplex account of single-item recency traditionally observed for backwards recognition testing of visual stimuli (Phillips & Christie, 1977).     

Sensory and semantic factors in recognition memory for odors and graphic stimuli: elderly versus young persons

In four experiments, young (18-26 years, M = 21) and elderly (over 65 years, M = 72) people were compared for recognition memory of (a) graphic stimuli (faces of presidents and vice presidents, engineering symbols, and free forms) and (b) everyday odors. On graphic stimuli, the elderly consistently matched the young, but on odors the performance of the elderly was worse. Their poorer olfactory performance was observed after only 26 s, but became truly marked after 1 hr or more. Somewhere between 1 hr and 2 weeks, their odor performance fell to chance, but their graphic performance remained well above chance. Although the young did forget both graphic and odor materials progressively, their performance always stayed above chance over a 6-month period. Experiments 1 and 2 revealed that the elderly are less sensitive to odors than the young (with thresholds about 10-fold higher), which may explain, in part, their poorer olfactory memory performance. Knowledge that the subjects brought to the tasks by way of familiarity with and ability to name odors and faces played a positive role in recognition memory. Because of this positive role, together with the negative role played by verbal distraction, we conclude that odor recognition memory depends, perhaps heavily, on semantic processing. Impaired semantic processing may result even when odors are simply rendered desaturated, or pastel because of the weakening of olfactory sensitivity with aging.     

Short- and long-term memory contributions to immediate serial recognition: Evidence from serial position effects

A long-standing body of research supports the existence of separable short- and long-term memory systems, relying on phonological and semantic codes, respectively. The aim of the current study was to measure the contribution of long-term knowledge to short-term memory performance by looking for evidence of phonologically and semantically coded storage within a short-term recognition task, among developmental samples. Each experimental trial presented 4-item lists. In Experiment 1 typically developing children aged 5 to 6 years old showed evidence of phonologically coded storage across all 4 serial positions, but evidence of semantically coded storage at Serial Positions 1 and 2. In a further experiment, a group of individuals with Down syndrome was investigated as a test case that might be expected to use semantic coding to support short-term storage, but these participants showed no evidence of semantically coded storage and evidenced phonologically coded storage only at Serial Position 4, suggesting that individuals with Down syndrome have a verbal short-term memory capacity of 1 item. Our results suggest that previous evidence of semantic effects on “short-term memory performance” does not reflect semantic coding in short-term memory itself, and provide an experimental method for researchers wishing to take a relatively pure measure of verbal short-term memory capacity, in cases where rehearsal is unlikely.