Biomedical subjects

Christopher Jarrold

Publications and source records attributed to Christopher Jarrold.

18 recordsLinked to original sources

PubMed2006

The problem with using eye-gaze to infer desire: a deficit of cue inference in children with autism spectrum disorder?

Children with autism respond atypically to eye-gaze cues, arguably because they fail to understand that eye-gaze conveys mentalistic information. Three experiments investigated whether a difficulty in inferring desire from eye-gaze in autism reflects a failure to understand the mentalistic significance of eye-gaze, an inhibitory deficit or a deficit of cue inference. While there was an inhibitory component to the tasks, children with autism were no more affected by this than controls. In addition, individuals' impairment in inferring desire was not limited to social cues, but was also observed when desire was cued by more general cues. Consequently, children with autism may have a general deficit in using arbitrary cues to make inferences, which impacts particularly on their social development.

Adolescent↗

PubMed2005

Evidence for unusual spatial location coding in Williams syndrome: an explanation for the local bias in visuo-spatial construction tasks?

Individuals with Williams syndrome (WS) display poor visuo-spatial cognition relative to verbal abilities. Furthermore, whilst perceptual abilities are delayed, visuo-spatial construction abilities are comparatively even weaker, and are characterised by a local bias. We investigated whether this differentiation in visuo-spatial abilities can be explained by a deficit in coding spatial location in WS. This can be measured by assessing participants' understanding of the spatial relations between objects within a visual scene. Coordinate and categorical spatial relations were investigated independently in four participant groups: 21 individuals with WS; 21 typically developing (TD) children matched for non-verbal ability; 20 typically developing controls of a lower non-verbal ability; and 21 adults. A third task measured understanding of visual colour relations. Results indicated first, that the comprehension of categorical and coordinate spatial relations is equally poor in WS. Second, that the comprehension of visual relations is also at an equivalent level to spatial relational understanding in this population. These results can explain the difference in performance on visuo-spatial perception and construction tasks in WS. In addition, both the WS and control groups displayed response biases in the spatial tasks. However, the direction of bias differed across the groups. This finding is explored in relation to current theories of spatial location coding.

Adult↗

PubMed2005

Impaired verbal short-term memory in Down syndrome reflects a capacity limitation rather than atypically rapid forgetting.

Individuals with Down syndrome suffer from relatively poor verbal short-term memory. Recent work has indicated that this deficit is not caused by problems of audition, speech, or articulatory rehearsal within the phonological loop component of Baddeley and Hitch's working memory model. Given this, two experiments were conducted to investigate whether abnormally rapid decay underlies the deficit. In a first experiment, we attempted to vary the time available for decay using a modified serial recall procedure that had both verbal and visuospatial conditions. No evidence was found to suggest that forgetting is abnormally rapid in phonological memory in Down syndrome, but a selective phonological memory deficit was indicated. A second experiment further investigated possible problems of decay in phonological memory, restricted to item information. The results indicated that individuals with Down syndrome do not show atypically rapid item forgetting from phonological memory but may have a limited-capacity verbal short-term memory system.

Adult↗

PubMed2005

Differential constraints on the working memory and reading abilities of individuals with learning difficulties and typically developing children.

This study examined the factors that constrain the working memory span performance and reading ability of individuals with generalized learning difficulties. In the study, 50 individuals with learning difficulties (LD) and 50 typically developing children (TD) matched for reading age completed two working memory span tasks. Participants also completed independent measures of the processing and storage operations involved in each working memory span task and Raven's Coloured Progressive Matrices. The results showed that despite an equivalent level of working memory span, the relative importance of the constraints on working memory differed between the groups. In addition, working memory span was not closely related to word recognition or sentence comprehension performance in the LD group. These results suggest that the working memory span performance of LD and TD individuals may reflect different working memory limitations and that individuals with generalized learning difficulties may approach cognitive tasks in a qualitatively different way from that of typically developing individuals.

Child↗

PubMed2005

Mapping the developmental constraints on working memory span performance.

This study investigated the constraints underlying developmental improvements in complex working memory span performance among 120 children of between 6 and 10 years of age. Independent measures of processing efficiency, storage capacity, rehearsal speed, and basic speed of processing were assessed to determine their contribution to age-related variance in complex span. Results showed that developmental improvements in complex span were driven by 2 age-related but separable factors: 1 associated with general speed of processing and 1 associated with storage ability. In addition, there was an age-related contribution shared between working memory, processing speed, and storage ability that was important for higher level cognition. These results pose a challenge for models of complex span performance that emphasize the importance of processing speed alone.

Age Factors↗

PubMed2005

Embedded figures detection in autism and typical development: preliminary evidence of a double dissociation in relationships with visual search.

Individuals with autism show relatively strong performance on tasks that require them to identify the constituent parts of a visual stimulus. This is assumed to be the result of a bias towards processing the local elements in a display that follows from a weakened ability to integrate information at the global level. The results of the current study showed that, among children with autism, ability to locate a figure embedded in a larger stimulus was only related to performance on visual search trials where the target was identified by a unique perceptual feature. In contrast, control children's embedded figures performance was specifically related to their performance on visual search trials where the target was defined by a conjunction of features. This double dissociation suggests that enhanced performance on perceptual tasks by children with autism is not simply a consequence of a quantitative difference in ability to engage in global processing.

Adolescent↗

PubMed2005

Serial order reconstruction in Down syndrome: evidence for a selective deficit in verbal short-term memory.

BACKGROUND: Individuals with Down syndrome consistently perform less well than appropriately matched comparison groups on tests of verbal short-term memory, despite performing relatively well on non-verbal short-term memory tasks. However, it is not clear whether these findings constitute evidence for a selective deficit in verbal short-term memory, or whether they instead reflect the influence of non-central factors such as speech difficulties or poor number knowledge. METHODS: Twenty-six individuals with Down syndrome and 32 typically developing children were tested on a digit reconstruction task in which participants were presented with auditory digit sequences and responded by pressing the corresponding digits on a touch-screen in the correct serial order. Background measures were performance on a closely matched visuo-spatial reconstruction task, reaction time on a simple digit identification task, receptive vocabulary age and non-verbal ability (Raven's matrices). Participants were also tested on a conventional digit recall task. RESULTS: All four background measures accounted for significant individual variation in digit reconstruction performance, but there remained a significant effect of group that reflected relatively poor performance of individuals with Down syndrome. Hierarchical regression showed that group membership accounted for unique variation in both digit reconstruction and recall performance, even after all group differences on background measures had been accounted for. CONCLUSIONS: The results provide strong evidence that Down syndrome is associated with a selective deficit in verbal short-term memory, and a deficit in verbal serial order memory in particular. Implications for the language difficulties associated with Down syndrome are discussed.

Adolescent↗

PubMed2004

Comprehension of spatial language terms in Williams syndrome: evidence for an interaction between domains of strength and weakness.

Individuals with Williams syndrome show an unusual neuropsychological profile, with relatively strong language abilities and impoverished visual and spatial abilities. Two studies are reported that examine the interaction between these two domains in Williams syndrome by assessing individuals' comprehension of spoken language with a spatial component. In a first study, the Test for Reception of Grammar (Bishop, 1983) was given to 32 individuals with Williams syndrome and to controls matched individually for total number of errors on the task. Individuals with Williams syndrome had particular problems when asked to comprehend sentences containing spatial prepositions, making significantly more errors on these items than control groups. A second study examined in more detail comprehension of sentences with spatial and non-spatial components, comparing the performance of 15 individuals with Williams syndrome and control groups matched for vocabulary ability. Individuals with Williams syndrome again showed impaired comprehension of spoken spatial terms. In contrast, they were unimpaired in comprehending utterances without a spatial component, with the exception of descriptions testing comprehension of non-spatial comparatives (lighter than and darker than). These results suggest that the spatial difficulties experienced by individuals with Williams syndrome may constrain language comprehension in certain circumstances. They also shed light on the ways in which spatial cognition may interact with language comprehension more generally.

Adolescent↗

PubMed2004

To match or not to match? Methodological issues in autism-related research.

Studies of autism typically adopt a factorial matched-groups design aimed at eliminating nonspecific factors such as mental retardation as explanations of performance on experimental tasks. This paper reviews the issues involved in designing such studies and interpreting their results and suggests that the best approach to matching may be to equate performance on carefully designed control tasks. However, we also argue that the interpretation of such studies is often complicated by the fact that associations between background measures and experimental task performance are not clear. Consequently, we also advocate the use of regression techniques that allow the researcher to determine the factors that relate to task performance and to assess the extent of group differences on the task of interest having taken these factors into account.

Autistic Disorder↗

PubMed2004

Language influences on verbal short-term memory performance in Down syndrome: item and order recognition.

Down syndrome is associated with severe deficits in language and verbal shortterm memory, but the causal relationship between these deficits is unclear. The current study therefore investigated the influence of language abilities on verbal short-term memory performance in Down syndrome. Twenty-one individuals with Down syndrome and 29 younger typically developing children were tested on memory for words and nonwords using 2 immediate recognition tasks: an order memory task that was a relatively pure measure of verbal short-term memory and an item memory task that was more sensitive to language ability. Despite having superior vocabulary knowledge to the typically developing children, individuals with Down syndrome were impaired on both order and item tasks. This impairment was particularly marked on the item task, where individuals with Down syndrome showed an atypically large lexicality effect. These results are interpreted in terms of an underlying verbal short-term memory deficit in Down syndrome that is compounded by poor phonological discrimination abilities.

Acoustic Stimulation↗

PubMed2003

Divided attention, selective attention and drawing: processing preferences in Williams syndrome are dependent on the task administered.

The visuo-spatial abilities of individuals with Williams syndrome (WS) have consistently been shown to be generally weak. These poor visuo-spatial abilities have been ascribed to a local processing bias by some [R. Rossen, E.S. Klima, U. Bellugi, A. Bihrle, W. Jones, Interaction between language and cognition: evidence from Williams syndrome, in: J. Beitchman, N. Cohen, M. Konstantareas, R. Tannock (Eds.), Language, Learning and Behaviour disorders: Developmental, Behavioural and Clinical Perspectives, Cambridge University Press, New York, 1996, pp. 367-392] and conversely, to a global processing bias by others [Psychol. Sci. 10 (1999) 453]. In this study, two identification versions and one drawing version of the Navon hierarchical processing task, a non-verbal task, were employed to investigate this apparent contradiction. The two identification tasks were administered to 21 individuals with WS, 21 typically developing individuals, matched by non-verbal ability, and 21 adult participants matched to the WS group by mean chronological age (CA). The third, drawing task was administered to the WS group and the typically developing (TD) controls only. It was hypothesised that the WS group would show differential processing biases depending on the type of processing the task was measuring. Results from two identification versions of the Navon task measuring divided and selective attention showed that the WS group experienced equal interference from global to local as from local to global levels, and did not show an advantage of one level over another. This pattern of performance was broadly comparable to that of the control groups. The third task, a drawing version of the Navon task, revealed that individuals with WS were significantly better at drawing the local form in comparison to the global figure, whereas the typically developing control group did not show a bias towards either level. In summary, this study demonstrates that individuals with WS do not have a local or a global processing bias when asked to identify stimuli, but do show a local bias in their drawing abilities. This contrast may explain the apparently contrasting findings from previous studies.

Adult↗

PubMed2003

The complexities of complex span: explaining individual differences in working memory in children and adults.

Two studies are presented that investigated the constraints underlying working memory performance in children and adults. In each case, independent measures of processing efficiency and storage capacity are assessed to determine their relative importance in predicting performance on complex span tasks,which measure working memory capacity. Results show that complex span performance was independently constrained by individual differences in domain-general processing efficiency and domain-specific storage capacity. Residual variance, which may reflect the ability to coordinate storage and processing, also predicted academic achievement. These results challenge the view that complex span taps a limited-capacity resource pool shared between processing and storage operations. Rather, they are consistent with a multiple-component model in which separate resource pools support the processing and storage functions of working memory.

Adult↗

PubMed2003

What are the causes of reduced fit in scaling and clustering studies of semantic proximity data, and how else to measure them: a comment on Storms et al. (2003).

G. Storms, T. Dirikx, J. Saerens, S. Verstraeten, and P. P. De Deyn (2003) noted that the goodness-of-fit indices for scaling and clustering solutions of proximity data from populations with hypothesized semantic deficits tend to be reduced in comparison with control participants, and that this precludes an unambiguous interpretation of such data. However, this effect is not necessarily as inconsistent with the proposal of semantic degradation in these groups, or as consistent with explanations in terms of access or attentional problems, as is suggested by G. Storms et al. Also, although performance on word fluency tasks is certainly constrained by the ability to access stored information, there are ways in which this confounding influence may be controlled for in the study of semantic deficits.

Cluster Analysis↗

PubMed2003

Visuospatial cognition in Williams syndrome: reviewing and accounting for the strengths and weaknesses in performance.

Individuals with Williams syndrome typically show relatively poor visuospatial abilities in comparison to stronger verbal skills. However, individuals' level of performance is not consistent across all visuospatial tasks. The studies assessing visuospatial functioning in Williams syndrome are critically reviewed, to provide a clear pattern of the relative difficulty of these tasks. This prompts a possible explanation of the variability in performance seen, which focuses on the processing demands of some of these tasks. Individuals with Williams syndrome show an atypical processing style on tests of construction, which does not affect tests of perception.

Humans↗

PubMed2003

A review of research into pretend play in autism.

Autism is currently diagnosed, in part at least, on the basis of problems in imagination. The article reviews the empirical evidence of difficulties in pretend play in autism, and focuses in particular on individuals' ability to engage in pretence in free play conditions, to produce pretence in more structured situations, and to make sense of pretend actions carried out by another person. These data suggest that individuals with autism have a marked difficulty in producing pretend play, but one that is reduced by providing substantial structure to the play situation or by testing comprehension of pretence. The implications of these findings for theories of pretend play in autism, in terms of an inability to conceive of non-literal situations, a difficulty in imposing a pretend usage on an object, or a failure to gain a benefit from engaging in pretend play, are discussed.

Autistic Disorder↗

PubMed2002

Verbal short-term memory in Down syndrome: a problem of memory, audition, or speech?

The current study explored three possible explanations of poor verbal short-term memory performance among individuals with Down syndrome in an attempt to determine whether the condition is associated with a fundamental verbal short-term memory deficit. The short-term memory performance of a group of 19 children and young adults with Down syndrome was contrasted with that of two control groups matched for level of receptive vocabulary. The specificity of a deficit was assessed by comparing memory for verbal and visuo-spatial information. The effect of auditory problems on performance was examined by contrasting memory for auditorily presented material with that for material presented both auditorily and visually. The influence of speech-motor difficulties was investigated by employing both a traditional recall procedure and a serial recognition procedure that reduced spoken response demands. Results confirmed that individuals with Down syndrome do show impaired verbal short-term memory performance for their level of receptive vocabulary. The findings also indicated that this deficit is specific to memory for verbal information and is not primarily caused by auditory or speech-production difficulties.

Adolescent↗

PubMedDate not supplied

Raven's matrices performance in Down syndrome: evidence of unusual errors.

The aim of this study was to investigate the types of errors produced by three participant groups (individuals with Down syndrome, with moderate learning disability, and typically developing children) whilst completing the Raven's Coloured Progressive Matrices task. An analysis of error categories revealed that individuals with Down syndrome produced a significantly different pattern of errors to the comparison groups. This difference remained, though was less marked, when the groups were matched on overall task performance. Consequently, even when the groups were making the same number of errors, they were not making the same type of errors. An investigation of age-related error patterns revealed that there was a significant change in the types of errors made by typically developing individuals with age. However, no significant age-related change was found in the types of errors made by participants with Down syndrome. The analysis also provided evidence that individuals with Down syndrome were not producing error types appropriate for their chronological age, or for their overall level of task performance. Possible explanations for these differences in terms of problems of integration of perceptual information, reduced visual acuity, and a lax criterion for task completion in Down syndrome are considered.

Adolescent↗

PubMedDate not supplied

The relationship between short-term memory and working memory: complex span made simple?

This experiment addresses the question of what makes a working memory measure a good predictor of higher-level abilities. Verbal and visuospatial processing episodes were interleaved with distinct verbal and visuospatial storage episodes to form four complex span tasks. Although these measures were reliable predictors of reading and mathematics ability in children, they were no more predictive of these abilities than corresponding simple span tasks involving storage alone. However, when individual differences in storage ability and processing capacity were controlled for, residual variance in complex span performance was related to academic ability in some cases. These findings indicate that complex span tasks are multiply determined, and that differences in task structure can dramatically influence the relative importance of these multiple constraints and the predictive power of a complex span measure.

Child↗