The company a word keeps: The role of neighbourhood density in verbal short-term memory.

Psycholinguistic information plays an important role in verbal short-term memory (vSTM). One such linguistic feature is neighbourhood density (ND)-the number of words that can be derived from a given word by changing a single phoneme or single letter-with vSTM performance typically better when word sequences are from dense rather than sparse neighbourhoods. This effect has been attributed to higher levels of supportive activation among dense neighbourhood words. Generally, it has been assumed that lexical variables influence item memory but not order memory, and we show that the typical vSTM advantage for dense neighbourhood words in serial recall is eliminated when using serial recognition. However, we also show that the usual effect of ND is reversed-for both serial recall and serial recognition-when using a subset of those same words. The findings call into question the way in which ND has been incorporated into accounts of vSTM that invoke mutual support from long-term representations on either encoding or retrieval.

Does short-term memory develop?

Such is the consistency by which performance on measures of short-term memory (STM) increase with age that developmental increases in STM capacity are largely accepted as fact. However, our analysis of a robust but almost ignored finding - that span for digit sequences (the traditional measure of STM) increases at a far greater rate than span for other verbal material - fundamentally undermines the assumption that increased performance in STM tasks is underpinned by developmental increases in capacity. We show that this digit superiority with age effect is explained by the relatively greater linguistic exposure to random sequences of digits versus other stimuli such as words. A simple associative learning process that learns incrementally from exposure to language accounts for the effect, without any need to invoke an STM mechanism, much less one that increases in capacity with age. By extension, using corpus data directed at 2-3 year old children, 4-6 year old children, and adults, we show that age-related performance increases with other types of verbal material are equally driven by the same basic associative learning process operating on the expanding exposure to language experienced by the child. Our results question the idea that tests such as digit span are measuring a dedicated system for the temporary maintenance and manipulation of verbal material, and as such have implications for our understanding of those aspects of typical and atypical development that are usually accounted for with respect to the operation of such a system.

Long-term associative learning predicts verbal short-term memory performance.

Studies using tests such as digit span and nonword repetition have implicated short-term memory across a range of developmental domains. Such tests ostensibly assess specialized processes for the short-term manipulation and maintenance of information that are often argued to enable long-term learning. However, there is considerable evidence for an influence of long-term linguistic learning on performance in short-term memory tasks that brings into question the role of a specialized short-term memory system separate from long-term knowledge. Using natural language corpora, we show experimentally and computationally that performance on three widely used measures of short-term memory (digit span, nonword repetition, and sentence recall) can be predicted from simple associative learning operating on the linguistic environment to which a typical child may have been exposed. The findings support the broad view that short-term verbal memory performance reflects the application of long-term language knowledge to the experimental setting.

Metamemory in a familiar place: The effects of environmental context on feeling of knowing.

Feeling-of-knowing (FOK) judgments are judgments of future recognizability of currently inaccessible information. They are known to depend both on the access to partial information about a target of retrieval and on the familiarity of the cue that is used as a memory probe. In the present study we assessed whether FOK judgments could also be shaped by incidental environmental context in which these judgments are made. To this end, we investigated 2 phenomena previously documented in studies on recognition memory-a context familiarity effect and a context reinstatement effect-in the procedure used to investigate FOK judgments. In 2 experiments, we found that FOK judgments increase in the presence of a familiar environmental context. The results of both experiments further revealed still higher FOK judgments when made in the presence of environmental context matching the encoding context of both cue and its associated target. The effect of context familiarity on FOK judgment was paralleled by an effect on the latencies of an unsuccessful memory search, but the effect of context reinstatement was not. Importantly, the elevated feeling of knowing in reinstated and familiar contexts was not accompanied by an increase in the accuracy of those judgments. Together, these results demonstrate that metacognitive processes are shaped by the overall volume of memory information accessed at retrieval, independently of whether this memory information is related to a cue, a target, or a context in which remembering takes place. (PsycINFO Database Record

Memory as embodiment: The case of modality and serial short-term memory.

Classical explanations for the modality effect-superior short-term serial recall of auditory compared to visual sequences-typically recur to privileged processing of information derived from auditory sources. Here we critically appraise such accounts, and re-evaluate the nature of the canonical empirical phenomena that have motivated them. Three experiments show that the standard account of modality in memory is untenable, since auditory superiority in recency is often accompanied by visual superiority in mid-list serial positions. We explain this simultaneous auditory and visual superiority by reference to the way in which perceptual objects are formed in the two modalities and how those objects are mapped to speech motor forms to support sequence maintenance and reproduction. Specifically, stronger obligatory object formation operating in the standard auditory form of sequence presentation compared to that for visual sequences leads both to enhanced addressability of information at the object boundaries and reduced addressability for that in the interior. Because standard visual presentation does not lead to such object formation, such sequences do not show the boundary advantage observed for auditory presentation, but neither do they suffer loss of addressability associated with object information, thereby affording more ready mapping of that information into a rehearsal cohort to support recall. We show that a range of factors that impede this perceptual-motor mapping eliminate visual superiority while leaving auditory superiority unaffected. We make a general case for viewing short-term memory as an embodied, perceptual-motor process.

The objects of visuospatial short-term memory: Perceptual organization and change detection.

We used a colour change-detection paradigm where participants were required to remember colours of six equally spaced circles. Items were superimposed on a background so as to perceptually group them within (a) an intact ring-shaped object, (b) a physically segmented but perceptually completed ring-shaped object, or (c) a corresponding background segmented into three arc-shaped objects. A nonpredictive cue at the location of one of the circles was followed by the memory items, which in turn were followed by a test display containing a probe indicating the circle to be judged same/different. Reaction times for correct responses revealed a same-object advantage; correct responses were faster to probes on the same object as the cue than to equidistant probes on a segmented object. This same-object advantage was identical for physically and perceptually completed objects, but was only evident in reaction times, and not in accuracy measures. Not only, therefore, is it important to consider object-level perceptual organization of stimulus elements when assessing the influence of a range of factors (e.g., number and complexity of elements) in visuospatial short-term memory, but a more detailed picture of the structure of information in memory may be revealed by measuring speed as well as accuracy.

Questioning short-term memory and its measurement: Why digit span measures long-term associative learning.

Traditional accounts of verbal short-term memory explain differences in performance for different types of verbal material by reference to inherent characteristics of the verbal items making up memory sequences. The role of previous experience with sequences of different types is ostensibly controlled for either by deliberate exclusion or by presenting multiple trials constructed from different random permutations. We cast doubt on this general approach in a detailed analysis of the basis for the robust finding that short-term memory for digit sequences is superior to that for other sequences of verbal material. Specifically, we show across four experiments that this advantage is not due to inherent characteristics of digits as verbal items, nor are individual digits within sequences better remembered than other types of individual verbal items. Rather, the advantage for digit sequences stems from the increased frequency, compared to other verbal material, with which digits appear in random sequences in natural language, and furthermore, relatively frequent digit sequences support better short-term serial recall than less frequent ones. We also provide corpus-based computational support for the argument that performance in a short-term memory setting is a function of basic associative learning processes operating on the linguistic experience of the rememberer. The experimental and computational results raise questions not only about the role played by measurement of digit span in cognition generally, but also about the way in which long-term memory processes impact on short-term memory functioning.

Limitless capacity: a dynamic object-oriented approach to short-term memory.

The notion of capacity-limited processing systems is a core element of cognitive accounts of limited and variable performance, enshrined within the short-term memory construct. We begin with a detailed critical analysis of the conceptual bases of this view and argue that there are fundamental problems - ones that go to the heart of cognitivism more generally - that render it untenable. In place of limited capacity systems, we propose a framework for explaining performance that focuses on the dynamic interplay of three aspects of any given setting: the particular task that must be accomplished, the nature and form of the material upon which the task must be performed, and the repertoire of skills and perceptual-motor functions possessed by the participant. We provide empirical examples of the applications of this framework in areas of performance typically accounted for by reference to capacity-limited short-term memory processes.

Continued effects of context reinstatement in recognition.

The context reinstatement effect refers to the enhanced memory performance found when the context information paired with a target item at study is re-presented at test. Here we investigated the consequences of the way that context information is processed in such a setting that gives rise to its beneficial effect on item recognition memory. Specifically, we assessed whether reinstating context in a recognition test facilitates subsequent memory for this context, beyond the facilitation conferred by presentation of the same context with a different study item. Reinstating the study context at test led to better accuracy in two-alternative forced choice recognition for target faces than did re-pairing those faces with another context encountered during the study phase. The advantage for reinstated over re-paired conditions occurred for both within-subjects (Exp. 1) and between-subjects (Exp. 2) manipulations. Critically, in a subsequent recognition test for the contexts themselves, contexts that had previously served in the reinstated condition were recognized better than contexts that had previously served in the re-paired context condition. This constitutes the first demonstration of continuous effects of context reinstatement on memory for context.

A matter of emphasis: Linguistic stress habits modulate serial recall.

Models of short-term memory for sequential information rely on item-level, feature-based descriptions to account for errors in serial recall. Transposition errors within alternating similar/dissimilar letter sequences derive from interactions between overlapping features. However, in two experiments, we demonstrated that the characteristics of the sequence are what determine the fates of items, rather than the properties ascribed to the items themselves. Performance in alternating sequences is determined by the way that the sequences themselves induce particular prosodic rehearsal patterns, and not by the nature of the items per se. In a serial recall task, the shapes of the canonical "saw-tooth" serial position curves and transposition error probabilities at successive input-output distances were modulated by subvocal rehearsal strategies, despite all item-based parameters being held constant. We replicated this finding using nonalternating lists, thus demonstrating that transpositions are substantially influenced by prosodic features-such as stress-that emerge during subvocal rehearsal.

Language and short-term memory: the role of perceptual-motor affordance.

The advantage for real words over nonwords in serial recall--the lexicality effect--is typically attributed to support for item-level phonology, either via redintegration, whereby partially degraded short-term traces are "cleaned up" via support from long-term representations of the phonological material or via the more robust temporary activation of long-term lexical phonological knowledge that derives from its combination with established lexical and semantic levels of representation. The much smaller effect of lexicality in serial recognition, where the items are re-presented in the recognition cue, is attributed either to the minimal role for redintegration from long-term memory or to the minimal role for item memory itself in such retrieval conditions. We show that the reduced lexicality effect in serial recognition is not a function of the retrieval conditions, but rather because previous demonstrations have used auditory presentation, and we demonstrate a robust lexicality effect for visual serial recognition in a setting where auditory presentation produces no such effect. Furthermore, this effect is abolished under conditions of articulatory suppression. We argue that linguistic knowledge affects the readiness with which verbal material is segmentally recoded via speech motor processes that support rehearsal and therefore affects tasks that involve recoding. On the other hand, auditory perceptual organization affords sequence matching in the absence of such a requirement for segmental recoding and therefore does not show such effects of linguistic knowledge.

Auditory distraction and perceptual organization: Streams of unconscious processing.

Perceptual organization is key to understanding auditory distraction. In order to achieve a fundamental understanding of distraction it is necessary to understand how auditory stimuli are perceived; specifically, how they are organized into entities that do not map directly onto simple single stimuli as defined by the experimenter. It is important not to mistake some arbitrary unit of analysis, such as the word, as the correct unit for understanding auditory processing; rather, the unit of the auditory object and its relative position to other auditory objects is the key to understanding distraction (as well as the whole of auditory cognition more generally). Here I provide two illustrative examples of auditory perceptual organization showing the superlative power of organizational principles: streaming by similarity and stimulus capture. I go on to show how these have been used to refine our understanding of distraction, and of the effects of distraction from sequences of sound, from single sounds, or single changes within a sequence. A common feature of work described here is that it compares the effects of different forms of organization: The nominal stimuli themselves are largely unchanged but the way they relate to each other can change distraction appreciably. That is, it is not the mere presence of sound that causes distraction but its organization and the way that relates to the currently prevailing activity.

Modalities of memory: is reading lips like hearing voices?

Functional similarities in verbal memory performance across presentation modalities (written, heard, lipread) are often taken to point to a common underlying representational form upon which the modalities converge. We show here instead that the pattern of performance depends critically on presentation modality and different mechanisms give rise to superficially similar effects across modalities. Lipread recency is underpinned by different mechanisms to auditory recency, and while the effect of an auditory suffix on an auditory list is due to the perceptual grouping of the suffix with the list, the corresponding effect with lipread speech is due to misidentification of the lexical content of the lipread suffix. Further, while a lipread suffix does not disrupt auditory recency, an auditory suffix does disrupt recency for lipread lists. However, this effect is due to attentional capture ensuing from the presentation of an unexpected auditory event, and is evident both with verbal and nonverbal auditory suffixes. These findings add to a growing body of evidence that short-term verbal memory performance is determined by modality-specific perceptual and motor processes, rather than by the storage and manipulation of phonological representations.