Max Coltheart

DRC: a dual route cascaded model of visual word recognition and reading aloud

This article describes the Dual Route Cascaded (DRC) model, a computational model of visual word recognition and reading aloud. The DRC is a computational realization of the dual-route theory of reading, and is the only computational model of reading that can perform the 2 tasks most commonly used to study reading: lexical decision and reading aloud. For both tasks, the authors show that a wide variety of variables that influence human latencies influence the DRC models latencies in exactly the same way. The DRC model simulates a number of such effects that other computational models of reading do not, but there appear to be no effects that any other current computational model of reading can simulate but that the DRC model cannot. The authors conclude that the DRC model is the most successful of the existing computational models of reading.

The MRC psycholinguistic database

This paper describes a computerised database of psycholinguistic information. Semantic, syntactic, phonological and orthographic information about some or all of the 98,538 words in the database is accessible, by using a specially-written and very simple programming language. Word-association data are also included in the database. Some examples are given of the use of the database for selection of stimuli to be used in psycholinguistic experimentation or linguistic research.

Varieties of developmental dyslexia

This paper reviews and evaluates the evidence for the existence of distinct varieties of developmental dyslexia, analogous to those found in the acquired dyslexic population. Models of the normal adult reading process and of the development of reading in children are used to provide a framework for considering the issues. Data from a large-sample study of the reading patterns of developmental dyslexics are then reported. The lexical and sublexical reading skills of 56 developmental dyslexics were assessed through close comparison with the skills of 56 normally developing readers. The results indicate that there are at least two varieties of developmental dyslexia, the first of which is characterised by a specific difficulty using the lexical procedure, and the second by a difficulty using the sublexical procedure. These subtypes are apparently not rare, but are relatively prevalent in the developmental dyslexic population. The results of a second experiment, which suggest that neither of these reading patterns can be accounted for in terms of a general language disorder, are then reported.

Iconic memory and visible persistence

There are three senses in which a visual stimulus may be said to persist psychologically for some time after its physical offset. First, neural activity in the visual system evoked by the stimulus may continue after stimulus offset (“neural persistence”). Second, the stimulus may continue to be visible for some time after its offset (“visible persistence”). Finally, information about visual properties of the stimulus may continue to be available to an observer for some time after stimulus offset (“informational persistence”). These three forms of visual persistence are widely assumed to reflect a single underlying process: a decaying visual trace that (1) consists of afteractivity in the visual system, (2) is visible, and (3) is the source of visual information in experiments on decaying visual memory. It is argued here that this assumption is incorrect. Studies of visible persistence are reviewed; seven different techniques that have been used for investigating visible persistence are identified, and it is pointed out that numerous studies using a variety of techniques have demonstrated two fundamental properties of visible persistence: theinverse duration effect (the longer a stimulus lasts, the shorter is its persistence after stimulus offset) and theinverse intensity effect (the more intense the stimulus, the briefer its persistence). Only when stimuli are so intense as to produce afterimages do these two effects fail to occur. Work on neural persistences is briefly reviewed; such persistences exist at the photoreceptor level and at various stages in the visual pathways. It is proposed that visible persistence depends upon both of these types of neural persistence; furthermore, there must be an additional neural locus, since a purely stereoscopic (and hence cortical) form of visible persistence exists. It is argued that informational persistence is defined by the use of the partial report methods introduced by Averbach and Coriell (1961) and Sperling (1960), and the term “iconic memory” is used to describe this form of persistence. Several studies of the effects of stimulus duration and stimulus intensity upon the duration of iconic memory have been carried out. Their results demonstrate that the duration of iconic memory is not inversely related to stimulus duration or stimulus intensity. It follows that informational persistence or iconic memory cannot be identified with visible persistence, since they have fundamentally different properties. One implication of this claim that one cannot investigate iconic memory by tasks that require the subject to make phenomenological judgments about the duration of a visual display. In other words, the so-called “direct methods” for studying iconic memory do not provide information about iconic memory. Another implication is that iconic memory is not intimately tied to processes going on in the visual system (as visible persistence is); provided a stimulus is adequately legible, its physical parameters have little influence upon its iconic memory. The paper concludes by pointing out that there exists an alternative to the usual view of iconic memory as a precategorical sensory buffer. According to this alternative, iconic memory is post-categorical, occurring subsequent to stimulus identification. Here, stimulus identification is considered to be a rapid automatic process which does not require buffer storage, but which provides no information about episodic properties of a visual stimulus. Information about these physical stimulus properties must, in some way, be temporarily attached to a representation of the stimulus in semantic memory; and it is this temporarily attached physical information which constitutes iconic memory.

Is there a causal link from phonological awareness to success in learning to read

In this review, we re-assess the evidence that phonological awareness represents a skill specific to spoken language that precedes and directly influences the process of reading acquisition. Longitudinal and experimental training studies are examined in detail, as these are considered most appropriate for exploring a causal hypothesis of this nature. A particular focus of our analysis is the degree to which studies to date have controlled for existing literacy skills in their participants and the influence that these skills might have on performance on phonological awareness tasks. We conclude that no study has provided unequivocal evidence that there is a causal link from competence in phonological awareness to success in reading and spelling acquisition. However, we believe that such a study is possible and outline some ideas for its design and implementation.

Modularity of music processing

The music faculty is not a monolithic entity that a person either has or does not. Rather, it comprises a set of neurally isolable processing components, each having the potential to be specialized for music. Here we propose a functional architecture for music processing that captures the typical properties of modular organization. The model rests essentially on the analysis of music-related deficits in neurologically impaired individuals, but provides useful guidelines for exploring the music faculty in normal people, using methods such as neuroimaging.

Does reading develop in a sequence of stages

Abstract This paper reviews and evaluates three recent stage theories of reading acquisition (Marsh, Friedman, Welch, & Desberg; Frith; Seymour) and also discusses the relationships between phonological awareness and reading, especially the direction of causality in such relationships. Data from a longitudinal study of reading acquisition are then reported. This study included assessments of phonological skills in children before they had begun to learn to read. The results of the study suggest that (a) even if learning to read is conceptualised as a sequence of stages, not all children pass through the same sequence of stages, (b) phonological awareness and reading acquisition have a reciprocal interactive causal relationship, not a unidirectional one, and (c) phonological skills can play a role in the very first stage of learning to read among phonologically adept children. Hence, it is incorrect to claim that the first stage of learning to read always involves such non-phonological procedures as “logographic” processing.

358,534 nonwords: The ARC Nonword Database

The authors present a model of the phonotactic and orthographic constraints of Australian and Standard Southern British English monosyllables. This model is used as the basis for a web-based psycholinguistic resource, the ARC Nonword Database, which contains 358,534 monosyllabic nonwords—48,534 pseudohomophones and 310,000 non-pseudohomophonic nonwords. Items can be selected from the ARC Nonword Database on the basis of a wide variety of properties known or suspected to be of theoretical importance for the investigation of reading.

Monothematic Delusions: Towards a Two-Factor Account

We provide a battery of examples of delusions against which theoretical accounts can be tested. Then we identify neuropsychological anomalies that could produce the unusual experiences that may lead, in turn, to the delusions in our battery. However, we argue against Mahers view that delusions are false beliefs that arise as normal responses to anomalous experiences. We propose, instead, that a second factor is required to account for the transition from unusual experience to delusional belief. The second factor in the etiology of delusions can be described superficially as a loss of the ability to reject a candidate for belief on the grounds of its implausibility and its inconsistency with everything else that the patient knows, but we point out some problems that confront any attempt to say more about the nature of this second factor.

Modularity and cognition

Modularity is a concept central to cognitive science, and Fodors analysis of cognitive modularity in his book The Modularity Of Mind has been widely influential - but also widely misunderstood. It is often claimed that the possession of some or other system-property is a necessary condition for that system to be modular in Fodors sense, but Fodor made it clear that he was not proposing a definition of modularity, nor proposing any necessary conditions for the applicability of the term. He was simply suggesting a number of system properties that are typical of modular systems. I argue that it is nevertheless possible to derive a useful definition of modularity from the kinds of arguments put forward by Fodor: A cognitive system is modular when and only when it is domain-specific. Given any such proposed module, the other features of modularity discussed by Fodor should be dealt with as empirical issues: for each feature (innateness, for example), it is an empirical question whether or not the proposed module has that feature.