Offering predictive testing for Huntington disease in a medical genetics clinic: Practical applications

Predictive testing for Huntington disease is presently offered in a select few medical genetics centers in the United States. This is in part due to the labor intensive counseling and psychological testing suggested by the research protocols. We discuss some specific suggestions for establishing programs for Huntington disease predictive testing within pre-existing medical genetics clinics to encourage more centers to offer presymptomatic testing. This will allow more at risk individuals the opportunity to consider predictive testing and cut down the expenses of traveling to the few predictive testing centers that currently exist. The counseling principals will remain similar to those discussed here, even following the identification of the Huntington disease mutation.     

Unitarian validation of a mathematical problem-solving exercise for sales occupations

A content-related test construction strategy was employed as a means of yielding a test with criterion-related evidence of validity. Utilizing a national sample of field sales job incumbents, a group-based job analysis method was developed to identify job requirements. A content validity and concurrent criterion-related study were then conducted. The results demonstrated both content and criterion-related evidence of validity. Differential validity by race or gender was not found. A comparison between minority and non-minority group regression lines found no statistically significant difference between slopes. However, a statistically significant difference between minority and non-minority intercept values was found. The results are discussed in respect to their consistency with other research findings. The significance of the study is addressed in light of the recent Unitarian approach towards the theoretical and practical nature of test validity. It is suggested that practitioners and researchers investigate further the elements of this research effort as guidance for satisfying professional and federal standards.     

On the comparison of TAT and free speech techniques in personality assessment

Schnurr, Rosenberg, and Oxman (1992) recently compared the free speech samples and Thematic Apperception Test (TAT) responses of 95 normal adults. They concluded that the two techniques are not interchangeable, and that the TAT, which proved superior in the prediction of individual differences, may be preferable to free speech instructions for eliciting data in content analytic studies. We disagree with both conclusions. Various forms of narrative speech samples may be highly correlated, so long as psychologically meaningful, well-validated, and higher order content categories are used. The use of first-order content categories is less likely to contribute to the study of personality.     

Unit price as a useful metric in analyzing effects of reinforcer magnitude.

In this paper, we applied the behavioral-economic concept of unit price to the study of reinforcer magnitude in an attempt to provide a consistent account of the effects of reinforcer magnitude on behavior. Recent research in the experimental analysis of behavior and in behavioral pharmacology suggests that reinforcer magnitude interacts with the schedule of reinforcement to determine response rate and total consumption. The utility of the unit-price concept thus stems from its ability to quantify this interaction as a cost-benefit ratio (i.e., unit price = characteristics of the schedule of reinforcement divided by magnitude of reinforcement). Research employing the unit-price concept has shown that as unit price increases, a positively decelerating function exists for consumption (i.e., a function with an increasingly negative slope, when plotted on log coordinates) and a bitonic function exists for response rate. Based on these findings, the present analysis applied the unit-price concept to those studies of reinforcer magnitude and drug self-administration that examined the effects of reinforcer magnitude on response rate using simple schedules of reinforcement (e.g., fixed-ratio schedule). This resulted in three findings: (a) Reinforcer-magnitude manipulations and schedule manipulations interact in a manner that can be quantified in terms of unit price as benefit and cost factors, respectively; (b) different reinforcer-magnitude manipulations are functionally interchangeable as benefit factors in the unit-price ratio; and (c) these conclusions appear warranted despite the differences in reinforcers (food or drug), species (dogs, monkeys, or rats), and schedules (interval or ratio), and despite the fact that these studies were not designed for a unit-price analysis. In methodological terms, these results provide further evidence that employing the unit-price concept is a parsimonious method for examining the effects of reinforcer magnitude. In theoretical terms, these results suggest that a single process may underlie the effect of combined reinforcer-magnitude and schedule manipulations.     

Accuracy and precision of the PEAK Performance Technologies Motion Measurement System

This study evaluated the accuracy and precision of the PEAK Performance Technologies, lnc.'s motion analysis system for three-dimensional angle reconstruction. Pendular motion of a bar, on which 18 retroreflective markers were mounted, was videotaped at three different orientations (parallel, and rotated 30 degrees right and left) to a plane at which two standard video cameras were aimed. The videotaped motion was digitized off-line, and 32 angles between the 18 markers were calculated. intraclass correlation coefficients (ICCs) were calculated between trials within each pendulum orientation and across orientations to determine system precision, and between randomly selected trials and actual angles to determine accuracy. lCCs were in all cases greater than.99. Within-trial standard deviations ranged between 0.05-0.8 degrees for the different angles. Deviations from the actual angle averaged 0.0-0.8 degrees across all angles and orientations. The results indicate that accurate and reliable angular measurements can be made with this motion analysis system.     

Predictors of stress in adolescents: an exploratory study of pregnant and of parenting females

A study of 152 adolescents enrolled in school-based programs for pregnant and parenting youth in Colorado in 1987-88 found no differences in overall stress levels between these two groups; however, salient predictors of stressful life events for pregnant teens were not the same as those for teen mothers. The mean age of study subjects was 16.5 years (range 14-19 years); most were living with a parent rather than the child's father. The dependent variable, level of stress, was measured through use of an abbreviated Life Events Questionnaire. Independent variables were assessed through administration of the Inventory of Social Supportive Behaviors, Rosenberg Self-Esteem Scale, and the Adolescent Coping Orientation for Problem Experiences scale. Of the 5 sources of stress measured (family, accidents, autonomy, deviance, relocation, and distress), only stress related to accidents differed significantly between pregnant and parenting adolescents. For pregnant adolescents, self-esteem was the only significant predictor of the overall level of stress; among parents, the only significant predictor was objective social support. Among adolescents, self-esteem was associated with more frequent use of social support and coping strategies. For parenting adolescents, self-esteem was correlated with the frequency of use of social support, satisfaction resulting from such use, and frequent use of coping strategies. Overall, the independent variables of social support, self-esteem, coping, and age were stronger predictors of stress in pregnant than in parenting adolescent females. This finding suggests that parenting teens may have successfully negotiated the multiple transitions involved in this new stage of the life-cycle. An important implication of this study is the need to design separate counseling components of school-based programs for pregnant versus parenting adolescents rather than to use a single curriculum.     

An X Windows tool for synthesizing face images from eigenvectors

An X Windows software tool for the construction of faces with a weighted combination of eigenvectors is described. The eigenvectors were extracted from an autoassociative matrix that comprised 100 face images. The program input consists of eigenvectors and sets of weights that describe individual faces and combines these to create face images. The tool creates a panel of buttons that permits the display of individual eigenvectors and the display of an average face as well. Facilities for on-line changes to the intensity of individual eigenvectors can be used to change the appearance of a face. Previously, O’Toole, Abdi, Deffenbacher, and Bartlett (1991) have shown that the intensity of certain individual eigenvectors contains reliable information for determining the sex and race of the face.     

Contextual effects on the ability of divers to use decompression tables

The present study compared the ability of novice divers to apply decompression tables having learnt how to use them in either the same or a different environment. Those subjects who had learnt how to use the tables in a different environment (i. e. had learnt on dry land and were tested underwater or vice-versa) performed on average 64 percent worse than those who had the same environment for both learning and test. This effect could not be ascribed to the disruption brought about by changing environments. The results show that contextual effects on memory extend beyond the recall of word lists (Godden and Baddeley, 1975) to the ability to implement potentially important instructions.     

An evaluation of the reliability of probability judgments across response modes and over time

Despite the importance of probability assessment methods in behavioral decision theory and decision analysis, little attention has been directed at evaluating their reliability and validity. In fact, no comprehensive study of reliability has been undertaken. Since reliability is a necessary condition for validity, this oversight is significant. The present study was motivated by that oversight. We investigated the reliability of probability measures derived from three response modes: numerical probabilities, pie diagrams, and odds. Unlike previous studies, the experiment was designed to distinguish systematic deviations in probability judgments, such as those due to experience or practice, from random deviations. It was found that subjects assessed probabilities reliably for all three assessment methods regardless of the reliability measures employed. However, a small but statistically significant decrease over time in the magnitudes of assessed probabilities was observed. This effect was linked to a decrease in subjects overconfidence during the course of the experiment.