Malingering in toxic exposure: classification accuracy of reliable digit span and WAIS-III Digit Span scaled scores

This study examined the sensitivity and false-positive error rate of reliable digit span (RDS) and the WAIS-III Digit Span (DS) scaled score in persons alleging toxic exposure and determined whether error rates differed from published rates in traumatic brain injury (TBI) and chronic pain (CP). Data were obtained from the files of 123 persons referred for neuropsychological evaluation related to alleged exposure to environmental and industrial substances. Malingering status was determined using the criteria of Slick, Sherman, and Iverson (1999). The sensitivity and specificity of RDS and DS in toxic exposure are consistent with those observed in TBI and CP. These findings support the use of these malingering indicators in cases of alleged toxic exposure and suggest that the classification accuracy data of indicators derived from studies of TBI patients may also be validly applied to cases of alleged toxic exposure.     

A Model-Based Approach to Understanding Apraxia in Corticobasal Syndrome

Limb apraxia is a neurological disorder of higher cognitive function characterized by an inability to perform purposeful skilled movements and not attributable to an elementary sensorimotor dysfunction or comprehension difficulty. Corticobasal Syndrome (CBS) is an akinetic rigid syndrome with asymmetric onset and progression with at least one basal ganglia feature (rigidity, limb dystonia or myoclonus) and one cortical feature (limb apraxia, alien hand syndrome or cortical sensory loss). Even though limb apraxia is highly prevalent in CBS (70–80%), very few studies have examined the performance of CBS patients on praxis measures in detail. This review aims to (1) briefly summarize the clinical, neuroanatomical and pathological findings in CBS, (2) briefly outline what limb apraxia is and how it is assessed, (3) to comprehensively review the literature on limb apraxia in CBS to date and (4) to briefly summarize the literature on other forms of apraxia, such as limb-kinetic apraxia and buccofacial apraxia. Overall, the goal of the review is to bring a model-based perspective to the findings available in the literature to date on limb apraxia in CBS.     

Absence of a sex difference in algorithms for spatial problem solving

Pairs of stimuli taken from a pscyhometric measure of spatial aptitude were shown to 36 college men and 32 college women. The stimuli in pairs were (a) either identical or mirror images, and (b) presented in orientations that differed by 0–135 deg. Individuals judged, as rapidly as possible, if the stimuli in a pair would be identical or mirror images if presented at the same orientation. Replicating previous work, there was a sex difference in the speed with which problems were solved. Of greater interest was the fact that men and women were quite alike in the frequency with which they used different algorithms to solve the problems. Most individuals solved the problems using an algorithm in which an individual encodes the stimuli in working memory, mentally rotates one stimulus to the orientation of the other, compares both determine if they are identical, and responds. Two variants of this algorithm were also used by some subjects. In one variant, if comparison revealed that the stimuli were dissimilar, individuals did not respond immediately but continued processing until a self- imposed deadline was reached. In another variation, subjects only rotated the comparison stimuli when their orientations exceeded a critical angle.     

A diagrammatic approach to computer instruction for the naive user

There are inherent difficulties with text as an instructional format. This research presents the development of a diagrammatic representation that overcomes some of those difficulties. A simple “language” is presented that includes both procedural and model information. This approach is applied to the instruction of word processing/text-editing skills. An experimental methodology is presented and preliminary results are reported that suggest that the diagrammatic approach results in improvements in both the amount of word processing accomplished and the speed with which modifications are made.     

The effects of instructional variables on young children's organization and free recall

The relationship between verbal instruction and children's free recall was examined. Sixty first-grade children (mean age 84 months) were trained to categorize pictures of common objects. Half were given organizational instructions emphasizing categorization, and half were given instructions emphasizing the individual objects. Similarly, half were given detailed verbal instructions and encouraged to listen, and half were taught using a question type format that encouraged participation. Immediately and after a 2- to 3-week delay, children who were shown an organizational strategy categorized the materials during study and attained higher recall scores than children who were shown a specific strategy. After the 2- to 3-week delay, children in the explanation groups out-performed children in the question-asking groups. The child's competence as measured by intelligence and performance in school did not contribute to amount recalled when subjects were given instructions emphasizing the general strategy. However, children of high competence benefited more from specific training by recalling more items than did children of low competence. These findings point to the importance of instructional variables in studying changes in children's processing capabilities.