Avoiding the problem state bottleneck by strategic use of the environment

We investigated whether environmental support can be used to circumvent the problem state bottleneck in human multitasking. Previously, it was shown that people can only maintain a single chunk of information in their problem state resource, the central part of working memory. Consequently, when the problem state resource was required by multiple tasks concurrently, performance decreased. This phenomenon was termed the problem state bottleneck. To investigate whether the environment can be used to circumvent this bottleneck, we conducted an experiment with two main conditions. In the No-Support condition we replicated an earlier experiment that indicated the existence of the problem state bottleneck. In the Support condition we presented external cues, reducing the load on the problem state resource. To support the results of the experiment we present a computational cognitive model. The experiment and model indicated that the problem state bottleneck can be avoided by using external cues. However, subjects only used external cues when this led to faster behavior. These results were interpreted in the light of the Soft Constraints Hypothesis, which states that humans always follow the fastest strategy possible, as opposed to the most accurate strategy.     

Mothers' and fathers' coping with chronic childhood disease

Abstract

Mothers and fathers with a child with diabetes, asthma, cardiac conditions, epilepsy or leukaemia completed questionnaires to investigate their appraisal of disease-related difficulties and patterns of coping. There were differences both in appraised difficulties and coping patterns as a function of diagnostic group. In general, mothers who perceived more difficulties reported that it was helpful to cope by gaining disease-related knowledge. Fathers who perceived more difficulties reported it was more helpful to adopt strategies to enhance their own personal autonomy. Fathers who perceived more difficulties also reported that contact with medical staff was less helpful. Implications are discussed in terms of the differential implications of coping with chronic childhood diseases for mothers and fathers. Theoretical models need to take into account the differential demands of specific diseases in accounting for parents' stress appraisal and coping patterns.     

Impairments of Attention Following Childhood Traumatic Brain Injury

Attentional deficits are commonly reported following traumatic brain injury (TBI) in adults, although the occurrence of such problems is less well documented in young children. This study aimed to investigate residual attentional abilities associated with TBI during childhood, by examining a number of aspects of attention including sustained, focussed, and divided attention, attentional shift, and response inhibition. Eighteen children with a history of TBI, aged between 8 and 14 years and 18 non-injured matched controls participated in the study. Results show that attentional skills may be differentially impaired after TBI, with children who have sustained moderate-to-severe TBI exhibiting significant deficits on the following attentional domains: sustain, focus, and response inhibition. These findings support the view that attentional impairments following pediatric TBI, while not global, may be more generalized than those reported for adult samples, perhaps reflecting the relative immaturity of attentional skills at the time of injury.     

Construct Validity of Raven's Advanced Progressive Matrices for African and Non‐African Engineering Students in South Africa

We test the hypothesis that the Raven's Advanced Progressive Matrices has the same construct validity in African university students as it does in non‐African students by examining data from 306 highly select 17‐ to 23‐year olds in the Faculties of Engineering and the Built Environment at the University of the Witwatersrand (177 Africans, 57 East Indians, 72 Whites; 54 women, 252 men). Analyses were made of the Matrices scores, an English Comprehension test, the Similarities subscale from the South African Wechsler Adult Intelligence Scale, end‐of‐year university grades, and high‐school grade point average. Out of the 36 Matrices problems, the African students solved an average of 23; East Indian students, 26; and White students, 29 (p<.001), placing them at the 60th, 71st, and 86th percentiles, respectively, and yielding IQ equivalents of 103, 108, and 118 on the 1993 US norms. The same pattern of group differences was found on the Comprehension Test, the Similarities subscale, university course grades, and high‐school grade‐point average. The items on the Matrices ‘behaved’ in the same way for the African students as they did for the non‐African students, thereby indicating the test's internal validity. Item analyses, including a confirmatory factor analysis, showed that the African/non‐African difference was most pronounced on the general factor of intelligence. Concurrent validity was demonstrated by correlating the Matrices with the other measures, both individually and in composite. For the African group, the mean r=.28, p<.05, and for the non‐African group, the mean r=.27, p<.05. Although the intercepts of the regression lines for the two groups were significantly different, their slopes were not. The results imply that scores on the Raven's Matrices are as valid for Africans as they are for non‐Africans.     

Construct validation of the Dutch version of the impact of event scale

The Impact of Event Scale (ES; M. J. Horowitz, N. Wilner, & W. Alvarez, 1979) is a worldwide-used self-report measure to assess the frequency of intrusive and avoidant phenomena after a variety of traumatic experiences. The purpose of this article is to assess the psychometric value of the Dutch version of the IES (D. Brom & R. J. Kleber, 1985) in several samples of individuals who had experienced various traumatic stressors. The reliability and structure of the IES were evaluated in 3 different samples (total N = 1.588). The reliability of the Dutch version of the IES was adequate across the various stressors. The construct validity was assessed by using confirmatory factor analyses. Outcomes revealed a robust structure over the various samples, generally supporting the composition of the original IES.     

The role of pattern recognition in children's exact enumeration of small numbers

Enumeration can be accomplished by subitizing, counting, estimation, and combinations of these processes. We investigated whether the dissociation between subitizing and counting can be observed in 4‐ to 6‐year‐olds and studied whether the maximum number of elements that can be subitized changes with age. To detect a dissociation between subitizing and counting, it is tested whether task manipulations have different effects in the subitizing than in the counting range. Task manipulations concerned duration of presentation of elements (limited, unlimited) and configuration of elements (random, line, dice). In Study 1, forty‐nine 4‐ and 5‐year‐olds were tested with a computerized enumeration task. Study 2 concerned data from 4‐, 5‐, and 6‐year‐olds, collected with Math Garden, a computer‐adaptive application to practice math. Both task manipulations affected performance in the counting, but not the subitizing range, supporting the conclusion that children use two distinct enumeration processes in the two ranges. In all age groups, the maximum number of elements that could be subitized was three. The strong effect of configuration of elements suggests that subitizing might be based on a general ability of pattern recognition.     

The dynamics of development on the Dimensional Change Card Sorting task

A widely used paradigm to study cognitive flexibility in preschoolers is the Dimensional Change Card Sorting (DCCS) task. The developmental dynamics of DCCS performance was studied in a cross-sectional design (N = 93, 3 to 5 years of age) using a computerized version of the standard DCCS task. A model-based analysis of the data showed that development on the DCCS task is best described as a discontinuous change in performance on the post-switch phase of the task. In addition to a perseveration group and a switch group, a transitional group that showed shifts between perseverating and switching during the post-switch trials could be distinguished. Computational models of performance and development on the DCCS task cannot, in their current forms, explain these results. We discuss how a catastrophe model of the developmental changes in task performance could be used to generate specific hypotheses about the variables that control development of DCCS performance.