Long-term spatial clustering in free recall

We explored the influence of space on the organisation of items in long-term memory. In two experiments, we asked our participants to explore a virtual environment and memorise discrete items presented at specific locations. Memory for those items was later on tested in immediate (T1) and 24 hours delayed (T2) free recall tests, in which subjects were asked to recall as many items as possible in any order. In experiment 2, we further examined the contribution of active and passive navigation in recollection dynamics. Results across experiments revealed a significant tendency for participants to consecutively recall items that were encountered in proximate locations during learning. Moreover, the degree of spatial organisation and the total number of items recalled were positively correlated in the immediate and the delayed tests. Results from experiment 2 indicated that the spatial clustering of items was independent of navigation types. Our results highlight the long-term stability of spatial clustering effects and their correlation with recall performance, complementing previous results collected in immediate or briefly delayed tests.     

Facilitation of free recall by categorical blocking depends on stimulus type

Items that are blocked by category are typically more memorable than unblocked items. We examined the blocking effect with different types of stimuli. In Experiment 1, subjects memorized either actual objects or the printed names of those objects. Free recall was enhanced significantly by blocking only in the printed name condition. In Experiment 2, it was demonstrated that these relationships occurred whether or not verbal labels are supplied for the stimulus items. The difference in the impact of blocking on free recall was hypothesized to reflect differences in the visual detail that characterized the stimulus items in the object and printed name conditions. To test this hypothesis, Experiment 3 was conducted, using four sets of stimulus items graded in visual detail. These were a set of objects, photographs of the objects, line drawings of the objects, and printed names of the objects. The visual detail hypothesis was supported.     

Effect of varying picture-sentence congruence on children's free recall.

70 fourth-grade children were shown objects arbitrarily arranged in an integrated scene. Subjects were randomly assigned to conditions which either presented a sentence that correctly labeled and correctly described the physical arrangement of the objects, presented a sentence containing the correct labels of the objects but not the correct physical arrangement, or presented a sentence which did not contain the correct labels and incorrectly described the physical arrangement. Control conditions either provided subjects with correct labels or omitted presentation of verbal prompts. Congruence between the object display and the sentence produced significantly higher recall and clustering than the incongruence or control conditions. The incongruence conditions did not produce significantly higher recall than the control conditions, suggesting that incongruence interferes with formation of stable grouping of items which appears to be an important factor in facilitating free recall.     

Effect of stimulus configuration on spatial judgments in search tasks

Although children over one year of age are able to code spatial information with respect to objects other than the self, there are many instances in which the self is inappropriately used as a spatial referent by children between 2 and 4 years of age. L. G. Braine and R. A. Eder (1983, Developmental Psychology, 19, 45-55) found that, in a search task, the nature of the array influenced the spatial referent used by 2-year-old children. The present work investigated the effect of varying the number, size, and arrangement of boxes in the array. It was found that only the number of boxes defining the left and right sides of the array influenced performance; that is, multiple boxes were associated with the use of external objects as spatial referents. These results were interpreted as stemming from the tendency of young children to code the location of an object with respect to nearby objects. This tendency would lead to the use of adjacent boxes and environmental objects as spatial referents for the multiple-box side, and the use of the self as a spatial referent for the single-box side.     

Effect of visual-verbal load and spatial compatibility on stimulus response

This study examined the effects of visual-verbalload (as measured by a visually presented reading-memory task with three levels) on a visual/auditory stimulus-response task. The three levels of load were defined as follows: "No Load" meant no other stimuli were presented concurrently; "Free Load" meant that a letter (A, B, C, or D) appeared at the same time as the visual or auditory stimulus; and "Force Load" was the same as "Free Load," but the participants were also instructed to count how many times the letter A appeared. The stimulus-response task also had three levels: "irrelevant," "compatible," and "incompatible" spatial conditions. These required different key-pressing responses. The visual stimulus was a red ball presented either to the left or to the right of the display screen, and the auditory stimulus was a tone delivered from a position similar to that of the visual stimulus. Participants also processed an irrelevant stimulus. The results indicated that participants perceived auditory stimuli earlier than visual stimuli and reacted faster under stimulus-response compatible conditions. These results held even under a high visual-verbal load. These findings suggest the following guidelines for systems used in driving: an auditory source, appropriately compatible signal and manual-response positions, and a visually simplified background.     

Primacy and recency effects in immediate free recall of sequences of spatial positions

This study evaluated the serial position curve based on free recall of spatial position sequences. To evaluate the memory processes underlying spatial recall, some manipulations were introduced by varying the length of spatial sequences (Exp. 1) and modifying the presentation rate of individual positions (Exp. 2). A primacy effect emerged for all sequence lengths, while a recency effect was evident only in the longer sequences. Moreover, slowing the presentation rate increased the magnitude of the primacy effect and abolished the recency effect. The main novelty of the present results is represented by the finding that better recall of early items in a sequence of spatial positions does not depend on the task requirement of an ordered recall but it can also be observed in a free recall paradigm.     

Effect of reutilization of retrieval cues on free recall of a text

Undergraduates, 20 women and 25 men, studied an expository text containing only isolated paragraphs. Each paragraph was accompanied by a potential retrieval cue. During the retention interval experimental subjects received a sentence-completion task or a new learning task in which half of these cues were used again. Processing of interpolated textual materials appeared generally to hamper access to the original text. Moreover, reutilization of cues appears to reduce their evocative power with respect to the original text.     

The anatomy of free recall

The relative importance of various covert cues used in free recall is inferred on the basis of conditional probabilities of free recall given success vs failure of cued recall of the same material. Thirty-six names associated with pictures arranged in a 6 by 6 matrix were learned. A free recall test of names was followed by cued recall of names, with pictures, positions, or joint pictures and positions used as cues. Matching tests based on these cues were also administered. The tests were given at one of two stages of training, immediately or after 2 days. Pictorial and position cues are equally well encoded, but pictorial cues are less accessible and, therefore, relatively more useful in cued recall than in free recall. Position and pictorial information related to the names appears to be encoded and forgotten independently, and there is no evidence for summation of subthreshold encoding effect.     

Understanding the dynamics of correct and error responses in free recall: Evidence from externalized free recall

The dynamics of correct and error responses in a variant of delayed free recall were examined in the present study. In the externalized free recall paradigm, participants were presented with lists of words and were instructed to subsequently recall not only the words that they could remember from the most recently presented list, but also any other words that came to mind during the recall period. Externalized free recall is useful for elucidating both sampling and postretrieval editing processes, thereby yielding more accurate estimates of the total number of error responses, which are typically sampled and subsequently edited during free recall. The results indicated that the participants generally sampled correct items early in the recall period and then transitioned to sampling more erroneous responses. Furthermore, the participants generally terminated their search after sampling too many errors. An examination of editing processes suggested that the participants were quite good at identifying errors, but this varied systematically on the basis of a number of factors. The results from the present study are framed in terms of generate-edit models of free recall.     

Association and categorisation effects on free recall

Lists of 18 words which varied in mean associative strength, the category membership of the associations and in word frequency were presented to subjects 3 times with recall required after each presentation. Recall efficiency increased with association level and with similarly categorised associates. In lists of High mean associative strength which consisted of similarly categorised words, the recall of high frequency word lists was facilitated but at low levels of associative strength, with similarly categorised words, recall was facilitated at both levels of word frequency used. Clustering and errors which were associatively related to the items being learned were greater in lists which contained sets of similarly categorised associates.     

Neurophysiological indices of free recall memory biases in major depression: The impact of stimulus arousal and valence

This study examined differential impact of the valence and arousal characteristics of stimuli on memory biases and brain activity in major depressive disorder (MDD) and non-depressed control participants. P300 and slow wave (SW) components of the event-related brain potential (ERP) were recorded in 18 MDD and 18 control individuals during the encoding of positive and negative, high and low arousal words in a free recall task. Control participants demonstrated expected enhanced memory for positive stimuli that was accompanied by a corresponding increase in SW ERP components. These effects were not seen in the MDD participants. Rather, memory biases for negative information in MDD were only observed for low arousal words and were not reflected in ERP amplitudes. This study suggests that the inconsistency in the MDD memory bias literature may be related to the arousing nature of the stimuli incorporated in the study.     

A note on the development of recall of spatial location

Recall of spatial location was studied with 5, 8, 12--13, and 17--18 year old subjects. Pictures of objects were shown one at a time in one of the four quadrants of a projection screen which was either blank (NF) or divided by a cross into four quadrants (F). The presence of the frame (F) did not affect item recall, but facilitated location recall more, the younger the subjects. Intentional learning of location was superior to incidental learning in the youngest but not in older children. The results are in agreement with Bryant's (1974) analysis of perceptual development which emphasizes the use of external spatial frames of reference in the encoding of attributes of visual objects in young children.     

Temporal encoding strategies result in boosts to final free recall performance comparable to spatial ones

The method of loci is a highly effective mnemonic that recruits existing salient memory for spatial locations and uses the information as a scaffold for remembering a list of items (Yates, 1966). One possible account for the effectiveness of the spatial method of loci comes from the perspective that it utilizes evolutionarily preserved mechanisms for spatial navigation within the hippocampus (Maguire et al. in Proceedings of the National Academy of Sciences, 97(8), 4398–4403, 2000; O’Keefe & Nadel, 1978; Rodriguez et al. in Brain Research Bulletin, 57(3), 499–503, 2002). Recently, though, neurons representing temporal information have also been described within the hippocampus (Eichenbaum in Nature Reviews Neuroscience, 15(11), 732–744, 2014; Itskov, Curto, Pastalkova, & Buzsáki in The Journal of Neuroscience, 31(8), 2828–2834, 2011; MacDonald, Lepage, Eden, & Eichenbaum in Neuron, 71(4), 737–749, 2011; Mankin et al. in Proceedings of the National Academy of Sciences, 109(47), 19462–19467, 2012; Meck, Church, & Matell in Behavioral Neuroscience, 127(5), 642, 2013), challenging the primacy of spatial-based functions to hippocampal processing. Given the presence of both spatial and temporal coding mechanisms within the hippocampus, we predicted that primarily temporal encoding strategies might also enhance memory. In two different experiments, we asked participants to learn lists of unrelated nouns using the (spatial) method of loci (i.e., the layout of their home as the organizing feature) or using two novel temporal methods (i.e., autobiographical memories or using the steps to making a sandwich). Participants’ final free recall performance showed comparable boosts to the method of loci for both temporal encoding strategies, with all three scaffolding approaches demonstrating performance well above uninstructed free recall. Our findings suggest that primarily temporal representations can be used effectively to boost memory performance, comparable to spatial methods, with some caveats related to the relative ease with which participants appear to master the spatial versus temporal methods.