Acurious effect with reversed letters explained by a theory of schema

MRC Developmental Psychology Unit, Drayton House, Gordon Street, London, W.C.I., England It takes longer to find a normal N embedded in a context of reversed Ns than it takes to find a reversed N embedded in a context of normal Ns. This is true for other letters as well and can be explained by a theory of schema. This theory holds that there is a schema for the normal form of a letter based on past experience, and that this schema is not a static but a flexible construct which is sensitive to the immediate cognitive context. This property of the schema enables recognition even if the letter is presented in a deviating form. A deviation, such as mirror reversal, may at times be as acceptable as the normal form of the letter. This is the case when context stimuli in a scanning task consist of reversed letters. If the target stimulus is the normal form of the letter, it is more difficult to detect since both context and target are accepted as the same letter.     

Comprehension in "hyperlexic" readers

Mentally retarded children who can read aloud written words better than one would expect from their Mental Age are often called hyperlexic. The reading comprehension thought to be impaired in such children was investigated in four experiments. Mentally retarded advanced decoders, including autistic and nonautistic children, were compared with younger nonretarded children matched for Mental Age and Reading Age. Experiment 1 established that mildly mentally retarded readers could match sentences to pictures as well as could be expected from their verbal ability. This was the same whether they read the sentences or heard them. Experiment 2 demonstrated that only the more able retarded subjects, but not the less able ones, used sentence context in a normal way in order to pronounce homographs. Experiments 3 and 4 showed that these same more able children could extract meaning at both sentence and story level, and their performance was indistinguishable from that of normal controls. Hence, it is doubtful whether these advanced decoders should be called hyperlexic. In contrast, the readers of relatively low verbal ability performed much worse than their normal controls. Although they could be induced under certain conditions to read sentence-by-sentence rather than word-by-word, they did not do so spontaneously. Furthermore, they did not make use of already existing general knowledge in order to answer questions about the stories they had read. The ability to comprehend in terms of large units of meaning seems to be specifically impaired in these low verbal ability fluent readers. We suggest that it is this impairment that marks true hyperlexia. Since there were no differences between autistic and nonautistic readers on any of our tasks, we conclude that hyperlexia is not an autism-specific phenomenon.     

Learning and reminiscence as a function of target predictability in a two-dimensional tracking task

Twenty subjects performed one of two types of a two-dimensional tracking task for two 5-min sessions, separated by a 10-min rest. In task I, both the horizontal and the vertical components of target movement were unpredictable. In task II, the horizontal component of target movement was predictable (sinusoidal), while the vertical movement was unpredictable. There was no change in level of performance throughout the 10 min of practice on task I. For task II's predictable component, there were marked within- and between-session improvements in performance; whereas for the unpredictable component there was only a between-session improvement. It is proposed that, in these tracking tasks, improvement with practice depends on the development of programmed sequences of movement which can only occur for predictable target movements. Only after a rest do these programmed sequences become automatic, releasing spare attentional capacity for improving the performance of any unpredictable components of the task.     

The role of sensorimotor impairments in dyslexia: a multiple case study of dyslexic children

This study attempts to investigate the role of sensorimotor impairments in the reading disability that characterizes dyslexia. Twenty-three children with dyslexia were compared to 22 control children, matched for age and non-verbal intelligence, on tasks assessing literacy as well as phonological, visual, auditory and motor abilities. The dyslexic group as a whole were significantly impaired on phonological, but not sensorimotor, tasks. Analysis of individual data suggests that the most common impairments were on phonological and visual stress tasks and the vast majority of dyslexics had one of these two impairments. Furthermore, phonological skill was able to account for variation in literacy skill, to the exclusion of all sensorimotor factors, while neither auditory nor motor skill predicted any variance in phonological skill. Visual stress seems to account for a small proportion of dyslexics, independently of the commonly reported phonological deficit. However, there is little evidence for a causal role of auditory, motor or other visual impairments.     

Why specific developmental disorders are not specific: On-line and developmental effects in autism and dyslexia

In this paper we will suggest that impairments in domain-specific functions may have wide-ranging developmental effects which mimic domain-general impairments. This may explain why ‘pure’ cases of developmental disorders are rare. The understanding of autism and dyslexia has been advanced by theories postulating failure of a specific mechanism against a background of unimpaired general processing. Impairment in the mechanisms underlying ‘theory of mind’ in autism, and ‘phonology’ in dyslexia, predict and explain the pattern of poor and good performance on a range of experimental and real-life tasks. However, existing accounts deal largely with the on-line effects of modular deficits, and can be criticised as not truly developmental. Here we attempt to trace developmental or down-stream effects of specific impairments in mentalising and phonological processing. We argue that these modules act as vital gatekeepers in development. Important in this process is the interaction of cognition with socio-cultural environment, an effect well-illustrated by cross-language differences in dyslexia. We claim that consideration of these developmental effects makes clear why postulating specific impairments may be sufficient for explaining more general deficits.     

Prospects for a cognitive neuropsychology of autism: Hobson's choice

Leslie (1987b) proposed a new, metarepresentational model for the cognition of pretense. This model identified a cognitive component necessary for the normal development of a "theory of mind." In this article, the relation of the child's early affective sensitivities to this component is considered. Early affective sensitivities seem to be cognitively distinct from the metarepresentational component. Childhood autism provides an interesting opportunity to study this problem. Three theoretical possibilities for the pathogenesis of this condition are presented: (a) a basic affective disorder as proposed by Hobson (this issue, p. 114), (b) a basic affective disorder and a basic cognitive disorder jointly, and (c) a basic cognitive disorder. There is little evidence for Option a, and a growing body of evidence supports Option c. Option b is sidelined for the time being on grounds of parsimony. Leslie's original theoretical proposals are revised, and some resulting implications are presented for the future investigation of the cognitive neuropsychology of autism.     

Coming to terms: quantifying the benefits of linguistic coordination

Sharing a public language facilitates particularly efficient forms of joint perception and action by giving interlocutors refined tools for directing attention and aligning conceptual models and action. We hypothesized that interlocutors who flexibly align their linguistic practices and converge on a shared language will improve their cooperative performance on joint tasks. To test this prediction, we employed a novel experimental design, in which pairs of participants cooperated linguistically to solve a perceptual task. We found that dyad members generally showed a high propensity to adapt to each other's linguistic practices. However, although general linguistic alignment did not have a positive effect on performance, the alignment of particular task-relevant vocabularies strongly correlated with collective performance. In other words, the more dyad members selectively aligned linguistic tools fit for the task, the better they performed. Our work thus uncovers the interplay between social dynamics and sensitivity to task affordances in successful cooperation.     

Explaining delusions of control: the comparator model 20 years on

Over the last 20 years the comparator model for delusions of control has received considerable support in terms of empirical studies. However, the original version clearly needs to be replaced by a model with a much greater degree of sophistication and specificity. Future developments are likely to involve the specification of the role of dopamine in the model and a generalisation of its explanatory power to the whole range of positive symptoms. However, we will still need to explain why symptoms can be so variable and we still do not understand the origin of the most mysterious symptom of all: thought insertion.