Prahlad Gupta

Vocabulary Acquisition and Verbal Short-Term Memory: Computational and Neural Bases ☆ ☆☆ ★

In this paper, we explore the hypothesis that human vocabulary acquisition processes and verbal short-term memory abilities utilize a common cognitive and neural system. We begin by reviewing behavioral evidence for a shared set of processes. Next, we examine what the computational bases of such a shared system might be and how vocabulary acquisition and verbal short-term memory might be related in mechanistic terms. We examine existing computational models of vocabulary acquisition and of verbal short-term memory, concluding that they fail to adequately relate these two domains. We then propose an alternative model which accounts not only for the relationship between word learning and verbal short-term memory, but also for a wide range of phenomena in verbal short-term memory. Furthermore, this new account provides a clear statement of the relationship between the proposed system and mechanisms of language processing more generally. We then consider possible neural substrates for this cognitive system. We begin by reviewing what is known of the neural substrates of speech processing and outline a conceptual framework within which a variety of seemingly contradictory neurophysiological and neuropsychological findings can be accommodated. The linkage of the shared system for vocabulary acquisition and verbal short-term memory to neural areas specifically involved in speech processing lends further support to our functional-level identification of the mechanisms of vocabulary acquisition and verbal short-term memory with those of language processing. The present work thus relates vocabulary acquisition and verbal short-term memory to each other and to speech processing, at a cognitive, computational, and neural level.

Examining the relationship between word learning, nonword repetition, and immediate serial recall in adults.

Two experiments examined whether the association between word-learning, nonword repetition, and immediate serial recall observed in children also exists in normal adults. The experiments also introduce a novel paradigm for studying word-learning. Experiment 1 studied the performance of 52 adults in nonword repetition, immediate serial recall, and word-learning tasks, examining the correlation between these measures. The results indicate that the developmental relationships between all three abilities also exist in adults. Experiment 2 investigated the robustness of these results using different stimuli and a variant of the word-learning task, and it also examined performance in a visuospatial span task, to test an alternative account of the results of Experiment 1; the results from 58 adults provide further evidence that the developmental association between word-learning, nonword repetition, and immediate serial recall extends into adulthood. The theoretical implications of these findings are discussed in terms of alternative models of the relationship between these abilities.

Theoretical and computational analysis of skill learning, repetition priming, and procedural memory

This article analyzes the relationship between skill learning and repetition priming, 2 implicit memory phenomena. A number of reports have suggested that skill learning and repetition priming can be dissociated from each other and are therefore based on different mechanisms. The authors present a theoretical analysis showing that previous results cannot be regarded as evidence of a processing dissociation between skill learning and repetition priming. The authors also present a single-mechanism computational model that simulates a specific experimental task and exhibits both skill learning and repetition priming, as well as a number of apparent dissociations between these measures. These theoretical and computational analyses provide complementary evidence that skill learning and repetition priming are aspects of a single underlying mechanism that has the characteristics of procedural memory.

The left posterior superior temporal gyrus participates specifically in accessing lexical phonology

Impairments in phonological processing have been associated with damage to the region of the left posterior superior temporal gyrus (pSTG), but the extent to which this area supports phonological processing, independent of semantic processing, is less clear. We used repetition priming and neural repetition suppression during functional magnetic resonance imaging (fMRI) in an auditory pseudoword repetition task as a semantics-free model of lexical (whole-word) phonological access. Across six repetitions, we observed repetition priming in terms of decreased reaction time and repetition suppression in terms of reduced neural activity. An additional analysis aimed at sublexical phonology did not show significant effects in the areas where repetition suppression was observed. To test if these areas were relevant to real word production, we performed a conjunction analysis with data from a separate fMRI experiment which manipulated word frequency (a putative index of lexical phonological access) in picture naming. The left pSTG demonstrated significant effects independently in both experiments, suggesting that this area participates specifically in accessing lexical phonology.

EXPLORING THE RELATIONSHIP BETWEEN WORD PROCESSING AND VERBAL SHORT-TERM MEMORY: EVIDENCE FROM ASSOCIATIONS AND DISSOCIATIONS

Abstract A theory of the cognitive organisation of lexical processing, verbal short-term memory, and verbal learning is presented along with a summary of data that bear on this issue. We conceive of verbal STM as the outcome of processing that invokes both a specialised short-term memory and the lexical system. On this model, performance of verbal STM tasks depends on the integrity of lexical knowledge, access to that knowledge, and processes that encode serial order information.

Word learning, phonological short-term memory, phonotactic probability and long-term memory: towards an integrated framework

Word learning is studied in a multitude of ways, and it is often not clear what the relationship is between different phenomena. In this article, we begin by outlining a very simple functional framework that despite its simplicity can serve as a useful organizing scheme for thinking about various types of studies of word learning. We then review a number of themes that in recent years have emerged as important topics in the study of word learning, and relate them to the functional framework, noting nevertheless that these topics have tended to be somewhat separate areas of study. In the third part of the article, we describe a recent computational model and discuss how it offers a framework that can integrate and relate these various topics in word learning to each other. We conclude that issues that have typically been studied as separate topics can perhaps more fruitfully be thought of as closely integrated, with the present framework offering several suggestions about the nature of such integration.

Primacy and recency in nonword repetition

An increasing body of evidence suggests that nonword repetition is related to immediate serial memory (e.g., Baddeley, Gathercole, & Papagno, 1998; Gathercole & Baddeley, 1993). One possible account of this relationship is that a nonword is processed like a list when it is first encountered. If this is the case, it should be possible to detect serial position effects in repetition of single nonwords. Three experiments tested this prediction. Experiment 1 examined whether there would be syllable serial position primacy and recency effects in repetition of polysyllabic nonwords, and obtained both primacy and recency effects. Experiments 2 and 3 showed that these effects were not due to the controlled duration of the nonwords or the requirements of concurrent articulation or the procedure by which nonwords were created.

Connectionist Models and Linguistic Theory: Investigations of Stress Systems in Languages

We question the widespread assumption that linguistic theory should guide the formulation of mechanistic accounts of human language processing. We develop a pseudo-linguistic theory for the domain of linguistic stress, based on observation of the learning behavior of a perceptron exposed to a variety of stress patterns. There are significant similarities between our analysis of perceptron stress learning and metrical phonology, the linguistic theory of human stress. Both approaches attempt to identify salient characteristics of the stress systems under examination without reference to the workings of the underlying processor. Our theory and computer simulations exhibit some strikingly suggestive correspondences with metrical theory. We show, however, that our high-level pseudo-linguistic account bears no causal relation to processing in the perceptron, and provides little insight into the nature of this processing. Because of the persuasive similarities between the nature of our theory and linguistic theorizing, we suggest that linguistic theory may be in much the same position. Contrary to the usual assumption, it may not provide useful guidance in attempts to identify processing mechanisms underlying human language.

Space aliens and nonwords: stimuli for investigating the learning of novel word-meaning pairs.

We describe a set of pictorial and auditory stimuli that we have developed for use in word learning tasks in which the participant learns pairings of novel auditory sound patterns (names) with pictorial depictions of novel objects (referents). The pictorial referents are drawings of “space aliens,” consisting of images that are variants of 144 different aliens. The auditory names are possible nonwords of English; the stimulus set consists of over 2,500 nonword stimuli recorded in a single voice, with controlled onsets, varying from one to seven syllables in length. The pictorial and nonword stimuli can also serve as independent stimulus sets for purposes other than word learning. The full set of these stimuli may be downloaded fromwww.psychonomic.org/archive/.

Phonological memory and vocabulary learning in children with focal lesions

Eleven children with early focal lesions were compared with 70 age-matched controls to assess their performance in repeating non-words, in learning new words, and in immediate serial recall, a triad of abilities that are believed to share a dependence on serial ordering mechanisms (e.g.,; ). Results for the experimental group were also compared with other assessments previously reported for the same children by. The children with brain injury showed substantial impairment relative to controls in the experimental tasks, in contrast with relatively unimpaired performance on measures of vocabulary and non-verbal intelligence. The relationships between word learning, non-word repetition, and immediate serial recall were similar to those observed in several other populations. These results support previous reports that there are persistent processing impairments following early brain injury, despite developmental plasticity. They also suggest that word learning, non-word repetition, and immediate serial recall may be relatively demanding tasks, and that their relationship is a fundamental aspect of the cognitive system.