A dual-networks architecture of top-down control

Complex systems ensure resilience through multiple controllers acting at rapid and slower timescales. The need for efficient information flow through complex systems encourages small-world network structures. On the basis of these principles, a group of regions associated with top-down control was examined. Functional magnetic resonance imaging showed that each region had a specific combination of control signals; resting-state functional connectivity grouped the regions into distinct 'fronto-parietal' and 'cingulo-opercular' components. The fronto-parietal component seems to initiate and adjust control; the cingulo-opercular component provides stable 'set-maintenance' over entire task epochs. Graph analysis showed dense local connections within components and weaker 'long-range' connections between components, suggesting a small-world architecture. The control systems of the brain seem to embody the principles of complex systems, encouraging resilient performance.     

Socialization and cognition in children between the age of 18 and 24 months

A cross-cultural study of mother–child dyads was set up to test the hypothesis that sociocultural differences, mediated by variations of maternal intervention, influence the way in which the child manipulates objects and, thereby, his cognitive and social competences. Two series of observations were conducted with three groups of children aged 18–24 months (15 from the American middle class, 15 from French families and 15 from North African families—the last two groups both underprivileged): (a) ‘naturalistic’ observations of two systems of interaction (child–mother and child–children interaction) showed that each child is characterized by one type of object manipulation (protected, induced, activated or autonomous) and that maternal intervention varies with the sociocultural background; assessment of the child's behavioural sequences unravelled his strategies for solving and avoiding conflicts with his peers; (b) observations of the child with a standardized material permitted an evaluation of his cognitive competences for spontaneous problem-solving. Regarding the assumptions of our hypothesis, the results furnish the following conclusions: (1) social and cognitive competences are related to the object manipulation type. In all samples, children characterized by ‘activated’ and ‘autonomous’ manipulation obtain the better results; (2) maternal intervention differs among the samples depending on the sociocultural background; these differences (limitation and physical contact) do not correspond to differences in types of manipulation; (3) type of manipulation is an interactive construction; it characterizes the functioning of the mother–child dyad and its prevailing dynamics between permanence and change. ©1997 by John Wiley & Sons, Ltd.     

Testing unidimensionality in polytomous Rasch models

A fundamental assumption of most IRT models is that items measure the same unidimensional latent construct. For the polytomous Rasch model two ways of testing this assumption against specific multidimensional alternatives are discussed. One, a marginal approach assuming a multidimensional parametric latent variable distribution, and, two, a conditional approach with no distributional assumptions about the latent variable. The second approach generalizes the Martin-Löf test for the dichotomous Rasch model in two ways: to polytomous items and to a test against an alternative that may have more than two dimensions. A study on occupational health is used to motivate and illustrate the methods.The authors would like to thank Niels Keiding, Klaus Larsen and the anonymous reviewers for valuable comments to a previous version of this paper. This research was supported by a grant from the Danish Research Academy and by a general research grant from Quality Metric, Inc.     

Development of letter-specific processing: the effect of reading ability

During development, perceptual processing is tuned to inputs in the environment such that certain frequently encountered classes of stimuli are processed more effectively than similar comparison stimuli. Letters represent a class of stimuli that are encountered frequently in the environment, at least in literate cultures. Thus, the present study examined the development of letter-specific processing in children 6-19 years old by comparing the difference between performance on a letter-matching task and an unfamiliar non-letter-matching task in different subject groups. Results revealed an increase in letter-specific processing with development. Moreover, comparisons of letter-specific processing in groups of subjects matched either in age or reading ability indicate that the emergence of letter-specific processing is linked to increased reading skill, rather than increased age per se. Findings support theories of perceptual expertise, which suggest that skilled processing drives the specialization of perceptual mechanisms for certain classes of stimuli.     

Responding to a Challenging Perceptual-Motor Task as a Function of Level of Experiential Avoidance

The Psychological Record - Participants displaying high versus low levels of experiential avoidance as assessed by the Acceptance and Action Questionnaire (Hayes, Strosahl, et al., 2004) were...