Trevor A. Harley

A Critique of Top-down Independent Levels Models of Speech Production: Evidence from Non-plan-Internal Speech Errors*

A number of speech errors are examined which are difficult to account for by top-down serial processing models of speech production which hove independent levels of processing. In particular, most of these errors are characterized by the presence of an interfering element which is external to the utterance under current construction. This paper has two main aims: to classify these errors, and to examine the constraints upon them. It is found that phonological similarity between the target and intrusion is a major determinant of error occurrence. The consequences for models of speech production are discussed in a framework consisting of the architecture and control structure of those models. A particular model to account for these data is proposed, consisting of a spreading activation lexical network.

Phonological activation of semantic competitors during lexical access in speech production

Abstract Experimental evidence from picture-naming tasks suggests that lexical access in speech production (lexicalisation) occurs in two non-overlapping stages. Semantic information is used to access an abstract lexical form; only when this stage is complete does phonological realisation begin. Such experimental data are interpreted as evidence against connectionist models of lexicalisation. This paper argues that, counterintuitively, connectionist models are not inconsistent with these data. This proposal is supported by appropriate simulations. Interactive activation models of speech production have the additional advantage of accounting for speech error and other data.

Serial Control of Phonology in Speech Production: A Hierarchical Model

A dynamic oscillator-based model of the sequencing of phonemes in speech production (OSCAR) is described. An analysis of phoneme movement errors (anticipations, perseverations, and exchanges) from a large naturalistic speech error corpus provides a new set of data suitable for quantitative modeling and is used to derive a set of constraints that any speech-production model must address. The new computational model is shown to account for error type proportions, movement error distance gradients, the syllable-position effect, and phonological similarity effects. The model provides an alternative to frame-based accounts, serial buffer accounts, and associative chaining theories of serial order processing in speech.

List learning of second language vocabulary

The learning of second language vocabulary in lists of word pairs is a widespread practice. A basic practical question in this respect is whether it is more effective for nonfluent bilinguals to learn word pairs in first language–second language order (Ll–L2), or vice versa. To date, experimental psychology has not given a clear answer to this question, partly because it has not addressed the relevant issues directly. This article reviews some aspects of psychology that are relevant to L2 vocabulary list learning and reports on an experiment conducted with comprehensive (high) school students, aged 11–13, who were learning French. The experiment examined the presentation of vocabulary items to be learned. It was found that presenting items in L1–L2 order was the more versatile form of presentation if both production and comprehension of L2 items were required on the part of the learner. The theoretical implications of the findings, relating to the structure of the bilingual lexicon, are also discussed.

Tip-of-the-tongue states and lexical access in dementia.

We induced tip-of-the-tongue (TOT) states in elderly participants with probable Alzheimers disease (AD). We found that they experienced TOTs but, unlike control subjects, were unable to provide any information about the target word for which they were searching. The related words produced by the AD participants were almost all semantically related to the target, with very few phonological relatives. (Adults normally produce more phonological relatives than semantic.) We examine the relationship between the target and non-target words produced in terms of their syntactic category, frequency, and imageability. The results are discussed with regard to their implications for speech production models. We interpret the results in terms of a two-stage interactive account where the retrieval deficit in dementia lies between the semantic and lexical levels.

Effects of extraversion and self-report arousal on semantic priming: A connectionist approach.

Simulation and experimental data were used to test the hypothesis that extraversion and self-report arousal affect the spread of activation in a connectionist semantic network, assessed by priming of lexical decision. A simulation of network activation processes showed that individual differences in different network parameters predict different patterns of observable individual differences in response time. Two experiments using undergraduate Ss showed that extraversion and arousal interactively affect priming magnitude, irrespective of the time lag between prime and target word and of prime stimulus quality. The simulation data suggest that the personality erects obtained experimentally may be governed by a specific network parameter, individual differences in the level of random noise

Does Cognitive Neuropsychology have a future

Reflections stimulated by Rapp, B. (Ed.) (2001). ‘The handbook of cognitive neuropsychology: What deficits reveal about the human mind’. Philadelphia: Psychology Press.

Connectionist approaches to language disorders

Abstract This paper reviews the impact of connectionism upon our understanding of brain-damaged language performance, and attempts to explain why it is of importance for the neuropsychology of language. Connectionism is an approach to modelling cognitive processes using networks of interconnected, simple, neuron-like units. Behaviour emerges as the result of the interaction of these units. It has provided a new way of thinking about cognitive processing, emphasizing its low-level mechanisms. One supposed advantage of connectionism is its biological plausibility. It is possible to «lesion» these systems by destroying some of the units or the connections between them. It is claimed that lesions to connectionist models of particular cognitive systems result in the appropriate acquired disorders. For example, lesioning a connectionist model of reading and word pronunciation results in surface dyslexia. Connectionist models of surface and deep dyslexia, and of word substitutions in aphasia, are described in de...

Constraints Upon Word Substitution Speech Errors

We explore the features of a corpus of naturally occurring word substitution speech errors. Words are replaced by more imageable competitors in semantic substitution errors but not in phonological substitution errors. Frequency effects in these errors are complex and the details prove difficult for any model of speech production. We argue that word frequency mainly affects phonological errors. Both semantic and phonological substitutions are constrained by phonological and syntactic similarity between the target and intrusion. We distinguish between associative and shared-feature semantic substitutions. Associative errors originate from outside the lexicon, while shared-feature errors arise within the lexicon and occur when particular properties of the targets make them less accessible than the intrusion. Semantic errors arise early while accessing lemmas from a semantic-conceptual input, while phonological errors arise late when accessing phonological forms from lemmas. Semantic errors are primarily sensitive to the properties of the semantic field involved, whereas phonological errors are sensitive to phonological properties of the targets and intrusions.

Environmental contamination of normal speech

Environmentally contaminated speech errors occur when material derived from the speakers environment but irrelevant to the speakers intended utterance is erroneously incorporated into speech. Such material may include the names of objects at which speakers are looking, words that speakers are concurrently reading, segments of speech that speakers overhear, or properties of objects in the environment. It was found that although environmental contaminations display less phonological facilitation than other speech error types, they display some semantic facilitation. If the target item and interfering item are from the same syntactic category, a word substitution is more likely to result than a word blend, whereas if the items are from different categories, a blend is more likely. It is hypothesized that environmental contamination occurs at a high level of processing, but with a relatively late insertion point.