A novel contact-lens system to assess visual hemispheric asymmetries.

A soft contact-lens system for achieving unilateral visual stimulation in a free vision format is described. Initial testing with light transmittance and visual perimetry indicated that the lenses created artificial visual-field deficits. The efficacy of the lenses as a technique for lateralizing visual input was evaluated by examining within-subject differences in performance on two visuospatial tasks. Speed and accuracy of performance were greater with visual input directed to the right hemisphere. These data support the lens design as a useful alternative to tachistoscopic procedures and previous lens systems.     

Status of perfusion scintigraphy in the diagnostic strategy in cerebrovascular disorders and space-occupying lesions

The results of an evaluation of the perfusion scintigraphy findings of 350 hospitalised neurological patients and 55 more strictly selected neurosurgical patients with cerebrovascular complaints, revealed an accuraty of 83%, a sensitivity of 89%, and a specificity of 83%. The selection of the patients had no influence on the results as a whole. Compared with contrast-medium angiography, incorrect diagnosis must be expected in 17% of the cases. This includes erroneous negative findings in 10% of the cases. Grounds for misinterpretations are suggested, and the biological and methodological limitations of the method are set forth.     

The role of verbal ability in the processing of complex verbal information

Summary This study investigated the relation between psychometric mental-ability test scores and several reaction-time measures; a simple-reaction task, a choice-reaction task, the Posner and Mitchell (1967) letter-identification task, and a variation of the sentence-verification task. Scores on the Raven Advanced Progressive Matrices and the Verbal Subtest of the Scholastic Aptitude Test (SATV) were obtained. The less complex information-processing tasks replicate earlier studies in which general intelligence was only marginally related to reaction-time measures. The sentence-verification task systematically varied task complexity. Several direct and derived measures from the task were significantly correlated with psychometric mentalability measures. However, even though a number of precautions were taken to ensure that the sentence-verification task assessed purely verbal-processing efficiency, there was little evidence for an important task-specific relation between verification measures and verbal ability. Moreover, despite its relative verbal complexity, sentence verification did not reflect a greater relationship to verbal ability than other tasks did. Overall, the information-processing efficiency measures used in this study suggested a fairly general, rather than a task-specific, relationship to intellectual ability.The research presented in this paper was conducted while the first author was affiliated with the University of Georgia, U. S. A.     

On various causes of improper solutions in maximum likelihood factor analysis

In the applications of maximum likelihood factor analysis the occurrence of boundary minima instead of proper minima is no exception at all. In the past the causes of such improper solutions could not be detected. This was impossible because the matrices containing the parameters of the factor analysis model were kept positive definite. By dropping these constraints, it becomes possible to distinguish between the different causes of improper solutions. In this paper some of the most important causes are discussed and illustrated by means of artificial and empirical data.The author is indebted to H. J. Prins for stimulating and encouraging discussions.     

Sharing behavior and racial preference in children

Three groups of white children, 43 preschoolers and first-graders, 46 third-graders, and 44 fifth-graders, were asked to choose either a white child or a black child as a recipient of sharing and also as a companion for several social interaction situations ordered for social distance. The preschoolers and first-graders preferred to share and interact socially with the white child. The third-graders and the fifth-graders displayed a weaker preference for the white child over the black child on the sharing task, no preference in situations of high social distance, and a preference for the white child in situations of low social distance. The results from ancillary measures suggested that the choices of the younger children were motivated by a generalized color preference but that the choices of the older children were guided by an awareness of the social meaning of racial categories.The investigation was supported by the Research Advisory Council of East Tennessee State University.     

Cognitive deficits in compulsive checkers: An exploratory study

Compulsive-checking behavior can be conceptualized as resulting, in part, from a memory failure. In order to determine if memory difficulties are associated with compulsive checking, the performance of college-student checkers were compared with the performance of non-checkers on a number of cognitive tasks hypothesized to be relevant to understanding checking behavior. Using the Checking and Cleaning subscales of the Maudsley Obsessional-Compulsive Inventory, four groups of subjects were identified: (1) Cleaning Checkers (N = 13); (2) Noncleaning Checkers (N = 13); (3) Cleaning Noncheckers (N = 13); and (4) Noncleaning Noncheckers (N = 15). It was hypothesized that the cognitive deficits studied would characterize individuals with cheeking compulsions, but not persons with non-checking compulsions (i.e. Cleaning Noncheckers) or normal controls (i.e. Noncleaning Noncheckers). Compulsive checkers were found to have a poorer memory for prior actions than non-checkers and were also found to underestimate their ability at distinguishing memories of real and imagined events, a process referred to as reality monitoring. Both of these deficits were specific to compulsive checkers and can be viewed as contributing to the likelihood that an individual will engage in checking behavior. If an individual has difficulty in recalling whether an intended action has been executed, they may be inclined to engage in checking behavior to insure the intended action is carried out. Similarly, a tendency to underestimate reality-monitoring ability could result in increased checking behavior as the individual attempts to reduce his/her uncertainty over whether a previous behavior actually occurred or merely was thought to occur. It is concluded that the study of cognitive deficits in compulsive checking is a potentially fruitful avenue for further inquiry.