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Coltheart, M., Tree, J. J., & Saunders, S. J. (2010). Computational modeling
of reading in semantic dementia: comment on Woollams, Lambon Ralph, Plaut,
and Patterson (2007). Psychological Review, 117, 256-271.
Notes: Woollams, Lambon Ralph, Plaut, and Patterson reported detailed data
on reading in 51 cases of semantic dementia. They simulated some aspects of
these data using a connectionist parallel distributed processing (PDP)
triangle model of reading. We argue here that a different model of reading,
the dual route cascaded (DRC) model of Coltheart, Rastle, Perry, Langdon,
and Ziegler (2001), not only provides a more accurate simulation of these
aspects of reading in semantic dementia than does the PDP model but also
provides highly accurate simulations of other aspects of reading in this
disorder that the PDP approach has not simulated. We conclude that our
findings add to evidence both from simulations of normal skilled reading and
from simulations of other kinds of acquired dyslexia that the
nonconnectionist DRC model of reading offers a better account of normal and
disordered reading than the connectionist PDP models of reading
Coltheart, M., Saunders, S. J., & Tree, J. J. (2010). Computational
modelling of the effects of semantic dementia on visual word recognition.
Cognitive Neuropsychology, 27, 101-114.
Notes: Rogers, Lambon Ralph, Hodges, and Patterson (2004) studied
two-alternative forced-choice visual lexical decision performance in
patients with semantic dementia. With item pairs where the target word was
more "typical" (i.e., higher in bigram and trigram frequency) than the foil
(all foils were pseudohomophones), lexical decision performance was good and
was unaffected by word frequency. With item pairs where the target word was
less "typical" (i.e., lower in bigram and trigram frequency) than the foil,
lexical decision performance was worse and was affected by word frequency,
being particularly inaccurate when the word targets were low in frequency.
We show (using as materials all the monosyllabic items used by Rogers and
colleagues) that the same pattern of results occurs in the lexical decision
performance of the DRC (dual-route cascaded) computational model of reading
when the model is lesioned by probabilistic deletion of low-frequency words
from its orthographic lexicon. We consider that the PDP (parallel
distributed processing) computational model of reading used by Woollams,
Plaut, Lambon Ralph, and Patterson (2007) to simulate reading in semantic
dementia is not capable of simulating this lexical decision result. We take
this, in conjunction with previous work on computational modelling of
reading aloud in surface dyslexia, phonological dyslexia, and semantic
dementia using the DRC and PDP reading models, to indicate that the DRC
model does a better job than the PDP model in accounting for what is known
about the various forms of acquired dyslexia
Macquarie Centre for Cognitive Science, Macquarie University, Sydney, New
South Wales, Australia. max@maccs.mq.edu.au
Coltheart, M. (2006). John Marshall and the cognitive neuropsychology of
reading. Cortex, 42, 855-860.
Notes: Macquarie Centre for Cognitive Science, Macquarie University, Sydney,
Australia. max@maccs.mq.edu.au
Contemporary cognitive neuropsychology owes a great debt to John Marshall.
His pioneering work on acquired and developmental disorders of reading
established the principles by which cognitive-neuropsychological theorizing
operates as well as leading to a profound understanding of the nature of
reading disorders which has subsequently influenced their assessment and
treatment
Coltheart, M. (2006). Acquired dyslexias and the computational modelling of
reading. Cognitive Neuropsychology, 23, 96-109.
Notes: M. Coltheart, Macquarie Centre for Cognitive Science, Macquarie
University, Sydney, NSW 2109
Two current approaches to the computational modelling of reading are the
connectionist triangle model approach (parallel processing; distributed
representations; models developed via a connectionist training algorithm
such as backpropagation) and the DRC ("dual route cascaded") model (serial
processing components permitted; local representations; model architecture
specified by the modeller rather than acquired by a learning algorithm). One
way of testing such computational models is to lesion the computer programs
that instantiate the models and study how well the impaired reading of such
damaged models corresponds to the patterns of impaired reading seen in
people with acquired dyslexia. This is computational cognitive
neuropsychology. It has been used with both types of model in attempts to
simulate acquired surface dyslexia and acquired phonological dyslexia. The
results of this body of work currently favour the DRC model over
connectionist models developed within the triangle model framework.
Blazely, A. M., Coltheart, M., & Casey, B. J. (2005). Semantic impairment
with and without surface dyslexia: Implications for models of reading.
Cognitive Neuropsychology, 22, 695-717.
The two best-developed computational models of reading aloud, the DRC model
of Coltheart and colleagues and the connectionist attractor model of Plaut
and colleagues, offer very different views about the degree to which
semantic knowledge is involved in lexical processing, and hence make
differing predictions about how semantic impairment (as seen, for example,
in semantic dementia) will impact on lexical processing in clinical cases.
Two cases meeting the criteria for semantic dementia, PC and EM, were given
a battery of tests comprising comprehension tasks, a reading task, and a
visual word recognition (lexical decision) task. AD tasks used the same
target words allowing cross-test and cross-patient comparisons. Both cases
showed significant impairment of semantic memory, and word comprehension was
found to be related to the word frequency of the target words. PC
demonstrated poor reading of irregular words, with a surface dyslexic
pattern of reading aloud, and he performed poorly on the visual lexical
decision task. His ability to read irregular words was related to their
frequency and to his ability to comprehend them. In contrast, his visual
lexical decision performance was not reliably influenced by his
comprehension of the same words or by their frequency. EM demonstrated
essentially perfect reading aloud of irregular words and essentially perfect
visual lexical decision, despite her severe semantic impairment. The pattern
of performance shown by EM is consistent with the DRC model of reading, but
inconsistent with the connectionist attractor model and with the view,
associated with that model, that orthographic and phonological processes
cannot remain intact when semantic representations are degraded.
Coltheart, M. (2004). Are there lexicons? Quarterly Journal of
Experimental Psychology A,Human Experimental Psychology, 57, 1153-1171.
Notes: Macquarie University, Sydney, Australia. max@maccs.mq.edu.au
Many models of the processing of printed or spoken words or objects or faces
propose that systems of local representations of the forms of such
stimuli--lexicons--exist. This is denied by partisans of the
distributed-representation connectionist approach to cognitive modelling. An
experimental paradigm of key theoretical importance here is lexical decision
and its analogue in the domain of objects, object decision. How does each
theoretical camp account for our ability to perform these two tasks? The
localists say that the tasks are done by matching or failing to match a
stimulus to a local representation in a lexicon. Advocates of distributed
representations often do not seek to explain these two tasks; however, when
they do, they propose that patterns of activation evoked in a semantic
system can be used to discriminate between words and nonwords, or between
real objects and false objects. Therefore the distributed-representation
account of lexical and object decision tasks predicts that performance on
these tasks can never be normal in patients with an impaired semantic
system, nor in patients who cannot access semantics normally from the
stimulus domain being tested. However, numerous such patients have been
reported in the literature, indicating that semantic access is not needed
for normal performance on these tasks. Such results support the localist
form of modelling rather than the distributed-representation approach
Coltheart, M., Rastle, K., Perry, C., Langdon, R., & Ziegler, J. (2001).
DRC: a dual route cascaded model of visual word recognition and reading
aloud. Psychological Review, 108, 204-256.
Notes: Macquarie Centre for Cognitive Science, Macquarie University, Sydney,
NSW 2109, Australia. max@maccs.mq.edu.au
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 model's 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
Jackson, N. E. & Coltheart, M. (2001). Routes to reading success and
failure: Toward an integrated cognitive psychology of atypical reading.
New York: Psychology Press.
Notes: 225pp; 8 chapters. 1. Introduction. 2. Proximal and distal causes of
individual differences in reading. 3. Dual-route theories of reading. 4.
Acquired dyslexia. 5. Reading acquisition. 6. Reading acquisition
difficulties. 7. Prococious reading. 8. Conclusions
Coltheart, M. (2000). Deep dyslexia is right-hemisphere reading. Brain
and Language, 71, 299-309.
Notes: Department of Psychology, Macquarie University, Sydney, New South
Wales, 2109, Australia. max@currawong.bhs.mq.edu.au ; ABSTRACT: Two views
exist concerning the proper interpretation of the form of acquired dyslexia
known as deep dyslexia: (a) that it represents reading by a multiply damaged
left hemisphere reading system; (b) that it represents reading which relies
extensively on right-hemisphere orthographic and semantic processing. Price,
Howard, Patterson, Warburton, Friston, and Frackowiak (1998) have recently
reported a brain-imaging study whose results, they claim, "preclude an
explanation of deep dyslexia in terms of purely right-hemisphere word
processing." Their claim conflicts with the conclusions of previous
published work, which strongly supports the RH hypothesis, work which they
do not mention. Furthermore, I argue that their own results also favor the
RH hypothesis (even though they claim otherwise); indeed, their results
permit the formulation of a much more detailed version of the RH hypothesis
than has hitherto been possible. Hence I conclude that the right-hemisphere
interpretation of deep dyslexic reading remains the preferred explanation of
deep dyslexia.
Coltheart, M. (1998). Seven questions about pure alexia (letter-by-letter
reading). Cognitive Neuropsychology, 15, 1-6.
Notes: I discuss ways in which the subsequent papers offer answers to some
basic questions about pure alexia (letter- by-letter reading).Is the
disorder a homogeneous one? Is the relevant impairment specific to the
reading system or is it a more general visual impairment? What is the nature
and the locus of the letter-by-letter reader's impairment, within some
functional model of reading? What causes the patients to read
letter-by-letter? What contribution does the right hemisphere make? Why is
letter-by-letter reading accuracy affected by imageability (concreteness)?
Why do some letter-by- letter readers show covert processing and others not?
Stuart, M. & Coltheart, M. (1988). Does reading develop in a sequence of
stages? Cognition, 30, 139-181.
Coltheart, M. (1987). Deep dyslexia: a right-hemisphere hypothesis. In
M.Coltheart, K. Patterson, & J. C. Marshall (Eds.), Deep dyslexia (2
ed., pp. 326-380). London: Routledge & Kegan Paul.
Coltheart, M. (1987). Deep dyslexia: a review of the syndrome. In
M.Coltheart, K. Patterson, & J. C. Marshall (Eds.), Deep dyslexia (2
ed., pp. 22-47). London: Routledge & Kegan Paul.
Coltheart, M. (1987). Reading, phonological reading, and deep dyslexia. In
M.Coltheart, K. Patterson, & J. C. Marshall (Eds.), Deep dyslexia (2
ed., pp. 197-226). London: Routledge & Kegan Paul.
M.Coltheart (Ed.), Attention and performance XII. The psychology of
reading. Hove: Erlbaum.
K.E.Patterson,
J. C. Marshall, & M. Coltheart (Eds.), Surface dyslexia:
Neuropsychological and cognitive studies of phonological reading.
London: Erlbaum.
Coltheart, M. (1985). Right-hemisphere reading revisited. Behavioral and
Brain Sciences, 8, 363-365.
Besner, D. & Coltheart, M. (1979). Ideographic and alphabetic processing in
skilled reading of English.
Neuropsychologia, 17,
467-472.
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