Tim Shallice

Institute of Cognitive Neuroscience, University College, London, UK














Selected references


Buiatti, T., Skrap, M., & Shallice, T. (2012). Left- and right-hemisphere forms of phonological alexia. Cognitive Neuropsychology, 29, 531-549.
Notes: We studied the ability of patients with lesions arising from operation for an anterior or posterior (left or right) brain tumour to read a set of words and pronounceable nonwords. In line with previous works, we observed that damage to the left posterior or left anterior cortex can give rise to phonological alexia, where the reading performance of nonwords is affected more than that of words. More surprisingly, similar effects were found in the right posterior group. However, there were significant differences in the error types, for both complex and positional errors, between phonological alexic patients in the three location groups. The findings present difficulties for the position held by theorists of the triangle model that phonological alexia arises from impairments in the language production system or in a general-purpose orthographic-phonological translation system. They also pose new questions about the possible role of the right posterior cortex in letter sequence representation
Cognitive Neuroscience Sector, SISSA, Trieste, Italy

Rosazza, C., Appollonio, I., Isella, V., & Shallice, T. (2007). Qualitatively different forms of pure alexia. Cognitive Neuropsychology, 24, 393-418.
Notes: T. Shallice, International School for Advanced Studies (SISSA-ISAS), Trieste
In this study we investigated two patients with pure alexia, F.C. and L.D.S., in order to make inferences about how processes and levels involved in the early stage of visual word recognition are organized and how they can be selectively damaged. Moreover, we investigated whether pure alexia can be caused by different functional deficits. F.C. and L.D.S. were presented with tasks of letter processing and tasks of orthographic integration. There was a clear double dissociation between the pattern of performance of F.C. and L.D.S. F.C. was able to process single letters rapidly and accurately, but was unable to group together the letters that he had correctly identified. By contrast, L.D.S. was slower and more impaired at letter identification, but she could use letter groups to assist reading. Thus, two different forms of pure alexia emerged: F.C. has a higher level deficit in integrating letters, whereas L.D.S. has a lower level deficit in letter processing. The results support the assumption of a functional organization of the reading process that involves a series of orthographic units (i.e., single letters, sublexical letter groups, and the lexical unit), which can be selectively damaged. Finally, our data present difficulties for models of pure alexia that assume all patients to have a low-level processing deficit

Shallice, T. & Rosazza, C. (2006). Patterns of peripheral paralexia: pure alexia and the forgotten visual dyslexia? Cortex, 42, 892-897.
Notes: International School for Advanced Studies - SISSA-ISAS, Trieste, Italy. t.shallice@ucl.ac.uk
The concept of visual dyslexia put forward by Marshall and Newcombe (1973) is assessed. After a long period of neglect it was resurrected in the late 1990s in a narrow form. In the current paper it is proposed that a wider form of the functional syndrome is useful to include amongst other conditions attentional dyslexia and neglect dyslexia. The variety of sub-forms would correspond to the behavioural effects of the different ways in which the orthographic processing systems can be impaired. What distinguishes the broader form from pure alexia is that the patient lacks the capacity to use a serial letter processing strategy, and so interpretation of visual dyslexia in terms of the impairment to the orthographic processing systems is not contaminated by the use of a compensatory strategy that results in processing operations which are qualitatively very different from the normal and highly opaque. The lack of a serial letter processing strategy makes visual dyslexia a much more transparent functional syndrome

McLeod, P., Shallice, T., & Plaut, D. C. (2000). Attractor dynamics in word recognition: converging evidence from errors by normal subjects, dyslexic patients and a connectionist model. Cognition, 74, 91-114.
Notes: Department of Experimental Psychology, Oxford University, Oxford, UK. peter.mcleod@psy.ox.ac.uk ; ABSTRACT: People make both semantic and visual errors when trying to recognise the meaning of degraded words. This result mirrors the finding that deep dyslexic patients make both semantic and visual errors when reading aloud. We link the results with the demonstration that a recurrent connectionist network which produces the meaning of words in response to their spelling pattern produces this distinctive combination of errors both when its input is degraded and when it is lesioned. The reason why the network can simulate the errors of both normal subjects and patients lies in the nature of the attractors which it develops as it learns to map orthography to semantics. The key role of attractor structure in the successful simulation suggests that the normal adult semantic reading route may involve attractor dynamics

Behrmann, M. & Shallice, T. (1995). Pure alexia: A nonspatial visual disorder affecting letter activation. Cognitive Neuropsychology, 12, 409-454.
Notes: Several different interpretations have been offered to explain the mechanism giving rise to the linear relationship between word length and reading time shown by patients with pure alexia or letter-by-letter reading. One interpretation attributes this word length effect to a spatial impairment in which there is a left- right gradient of processing efficiency. This fundamental resource limitation requires that the patient focus on each letter in turn to increase its signal-to-noise ratio and discriminability, especially for letters towards the end of the string. An alternative view attributes the word length effect to a letter activation deficit that disrupts the rapid and efficient processing of single letters. In this paper, we examine these two hypotheses in relation to DS, a letter-by-letter reader. DS is able to distribute her attention to multiple locations in parallel and her performance is unaffected by the absolute or relative spatial location of the letters in a string. She is, however, impaired at reporting the identity of a letter independent of its spatial location and requires an abnormally long time to process each letter. Furthermore, investigations of DS's reading, using Howard's (1991) analyses of reaction time distributions, suggest that she processes each letter in a sequentially order. Based on the results of these studies, we propose that prototypic pure alexia is a nonspatial visual disorder that affects the activation of individual letters

Shallice, T. (1991). Precis of From neuropsychology to mental structure. Behavioral and Brain Sciences, 14, 429-437,457-469.
Notes: Neuropsychological results are increasingly cited in cognitive theories although their methodology has been severely criticised. The book argues for an eclectic approach but particularly stresses the use of single-case studies. A range of potential artifacts exists when inferences are made from such studies to the organisation of normal function - for example, resource differences among tasks, premorbid individual differences, and reorganisation of function. The use of "strong" and "classical" dissociations minimises potential artifacts. The theoretical convergence between findings from fields where cognitive neuropsychology is well developed and those from the normal literature strongly suggests that the potential artifacts are not critical. The fields examined in detail in this respect are short-term memory, reading, writing, the organisation of input and output speech systems, and visual perception. Functional dissociation data suggest that not only are input systems organised modularly, but so are central systems. This conclusion is supported by findings on impairment of knowledge, visual attention, supervisiory functions, memory and consciousness

G.Vallar & T. Shallice (Eds.), Neuropsychological impairments of short-term memory (pp. 477-508). Cambridge: Cambridge University Press.

Shallice, T. (1988). From neuropsychology to mental structure. Cambridge: Cambridge University Press.
Notes: 462 pp. 16 chapters organized in 4 parts: I.INTRODUCING COGNITIVE NEUROPSYCHOLOGY. 1.From the diagram makers to cognitive neuropsychology. 2.The cognitive neuropsychology approach. II.CONVERGING OPERATIONS: SPECIFIC SYNDROMES AND EVIDENCE FROM NORMAL SUBJECTS. 3.The short-term memory syndrome. 4.The peripheral dyslexias. 5.The central dyslexias. 6.The agraphias. 7.Language operations: Are input and output processes separate. 8.The generality of the approach: The case of visual perception. III.INFERENCES FROM NEUROPSYCHOLOGICAL FINDINGS. 9.On method: A rejection of ultra-cognitive neuropsychology. 10.On method: Single case studies. 11.Functional specialisation. IV.CENTRAL PROCESSES: EQUIPOTENTIALITY OR MODULARITY? 12.Selective impairments of knowledge. 13.The allocation and direction of processing resources: Visual attention. 14.The allocation of processing resources: Higher-level control. 15.Amnesia: What is memory for? 16.Modularity and consciousness

Shallice, T. & Warrington, E. K. (1987). Single and multiple component central dyslexic syndromes. In M.Coltheart, K. Patterson, & J. C. Marshall (Eds.), Deep dyslexia (2 ed., pp. 119-145). London: Routledge & Kegan Paul.

Shallice, T. & Saffran, E. (1986). Lexical processing in the absence of explicit word identification: Evidence from a letter-by-letter reader. Cognitive Neuropsychology, 3, 429-458.
Notes: The lexical decision performance of a letter-by-letter reader, ML, was analysed for words presented for too short an exposure duration for him to identify or name them. His level of performance was surprisingly good by comparison with that of previously reported patients. In addition he gave a very similar pattern of responses to inappropriately affixed words as to appropriately affixed ones. His performance on these tasks could not be attributed to neglect or to the use of letter sequential dependencies. In addition, with the same exposure duration, ML showed "semantic access" characteristics in word categorization tasks. This evidence for lexical processing in the absence of explicit identification is discussed in relation to alternative accounts of letter-by-letter reading.

Shallice, T. & McCarthy, R. (1985). Phonological reading: From patterns of impairment to possible procedures. In K.E.Patterson, J. C. Marshall, & M. Coltheart (Eds.), Surface dyslexia: Neuropsychological and cognitive studies of phonological reading (1 ed., pp. 361-397). London: Erlbaum.

Shallice, T., McLeod, P., & Lewis, K. (1985). Isolating cognitive modules with the dual-task paradigm: are speech perception and production separate processes? Quarterly Journal of Experimental Psychology A,Human Experimental Psychology, 37, 507-532.

Warrington, E. K. & Shallice, T. (1984). Category specific semantic impairments. Brain, 107, 829-854.
Notes: We report a quantitative investigation of the visual identification and auditory comprehension deficits of 4 patients who had made a partial recovery from herpes simplex encephalitis. Clinical observations had suggested the selective impairment and selective preservation of certain categories of visual stimuli. In all 4 patients a significant discrepancy between their ability to identify inanimate objects and inability to identify living things and foods was demonstrated. In 2 patients it was possible to compare visual and verbal modalities and the same pattern of dissociation was observed in both. For 1 patient, comprehension of abstract words was significantly superior to comprehension of concrete words. Consistency of responses was recorded within a modality in contrast to a much lesser degree of consistency between modalities. We interpret our findings in terms of category specificity in the organization of meaning systems that are also modality specific semantic systems

Shallice, T., Warrington, E. K., & McCarthy, R. (1983). Reading without semantics. Quarterly Journal of Experimental Psychology A,Human Experimental Psychology, 35, 111-138.
Notes: Analysis of the reading of a neurological patient (HTR) indicates that it is based on the operation of a relatively unimpaired phonological route. Quantitative investigations of type of error, reading speed and the effects of lexicality and spelling-to-sound regularity all support this conclusion. Spelling-to-sound regularity is shown to influence reading not only through regular words being read better than irregular, but also through mildly irregular words being better read than very irregular ones. A model is presented of the operation of the phonological route and of its progressive impairment in certain types of neurological disease

Shallice, T. & Coughlan, A. K. (1980). Modality specific word comprehension deficits in deep dyslexia. Journal of Neurology, Neurosurgery and Psychiatry, 43, 866-872.
Notes: A deep dyslexic patient was tested on a series of experiments designed to assess her comprehension of abstract words. On tests where a precise semantic representation of words was required, performance was much poorer with visual than with auditory presentation. However, on some but not all categorisation tests performance with both modalities was good. It is argued that deep dyslexia can result from a modality-specific deficit in attaining the meaning of words together with a disorder of the phonological reading route

Warrington, E. K. & Shallice, T. (1980). Word-form dyslexia. Brain, 103, 99-112.
Notes: In this study we have reported our investigation of two patients with an acquired dyslexia characterized by letter-by-letter reading, whole word reading being apparently impossible. It has been shown that this phenomenon of letter-by-letter reading cannot be accounted for by visual or perceptual factors nor by impairment of visual span of apprehension. The exceptionally slow speed of reading was documented and a clear relationship between word length and reading speed established. Performance on tasks considered to maximize whole word reading which at the same time prevent the possibility of letter-by-letter reading, namely, reading script and reading with tachistoscopic presentation, was impaired. The satisfactory performance of these two patients on tasks of picture interpretation suggests that the two components of the syndrome simultanagnosia, letter-by-letter reading and piecemeal perception of complex scenes, are dissociable. Three alternative explanations of letter-by-letter reading are considered and we conclude that in this type of acquired dyslexia there is damage to the system through which a visual word-form is attained

Warrington, E. K. & Shallice, T. (1979). Semantic access dyslexia. Brain, 102, 43-63.
Notes: An analytical investigation of the residual reading capacities of a single patient with dyslexia without dysgraphia is reported. Both his ability to name and to comprehend letters and words were severely impaired. The major finding of this investigation was AR's striking capacity for categorizing words he could not read. In addition there was evidence of semantic priming effects. Thus AR was frequently able to achieve partial comprehension of words he could not read. The orthodox interpretation of the dyslexia without dysgraphia in terms of a disconnection syndrome is shown to be inappropriate, at least for the present case, where the deficit appears to be within the semantic domain; it is argued that this type of dyslexia is due to an impairment in accessing semantic information

Shallice, T. & Warrington, E. K. (1975). Word recognition in a phonemic dyslexic patient. Quarterly Journal of Experimental Psychology, 27, 187-199.

Anders Gade