Degree Name

Master of Arts (MA)

Semester of Degree Completion

1982

Thesis Director

William T. Roberts

Abstract

Organicity screening devices are those psychometric tests used to detect brain dysfunction during the initial assessment. The characteristics of such tests were listed and ones currently being used were reviewed. The review concentrated on the validity and clinical utility of these organicity tests. From the review it was concluded that the validity has not been thoroughly established, partially because weak criteria have been used. It was also concluded that current screening tests have questionable clinical utility, since an inordinant number of organically impaired people are not detected by the tests. The concept of organicity was discussed, and the Tactual Performance Test was proposed as a new organicity screening test. A validation and cross-validation experiment was done by comparing the Tactual Performance Test with the Halstead-Reitan Battery, a more appropriate criterion. This study investigated the validity and utility of the test.

Data from the Tactual Performance Test and the Halstead-Reitan Battery were collected for 200 male veterans; these subjects were randomly selected from the neuropsychology archives at a VA Medical Center. Two groups of 100 subjects each served as the Validation and Cross-validation samples. The groups did not differ significantly in age or education; the mean age was 44.24 years and the mean education level was 10.97 years. To compare the Tactual Performance Test with the Halstead-Reitan Battery, the three test scores, age and education were chosen as independent variables, and the Average Impairment Rating from the battery was chosen as the dependent variable. For the Validation group the the variables were used to create a multiple regression equation which predicted the dependent variable. The independent variables for the Cross-validation group were entered into this equation to check its ability to predict the dependent variable. The validity of the Tactual Performance Test was judged by computing the multiple regression coefficient and the Pearson r for the two groups. The clinical utility of the test was judged by the overall accuracy and the number of Type I and Type II errors.

Of the five independent variables, age did not make a significant contribution to the predicted Average Impairment Rating; this variable was found to be a correlate of every other variable. The resultant equation was found very capable of predicting the dependent variable. The correlations for the Validation and Cross-validation groups were .85 and .86 respectively, each significant at the .001 level. The utility of the Tactual Performance Test and education was also impressive; there were 87% correct predictions for the Validation group and 86% correct for the Cross-validation group. In addition very few organically impaired individuals escaped detection by this method. Therefore the Tactual Performance Test is judged a valid and useful organicity screening device. Shortcomings of this study were discussed and a further study incorporating females was proposed.

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