The effect of word frequency on verbal preservation in dysphasia.

Abstract

Eight dysphasics read two 29 word lists. Both lists consisted of long nouns of high: concreteness, imagery, and meaningfulness. Words on one list were all of a high frequency (100 or more occurrences per million). Words on the other list occurred only from one to ten times per million on the Thorndike-Lorge word frequency list. Rates of verbal perseveration, number of correct responses and response latencies were examined on the two lists. The only significant difference was found on the number of correct responses. Subjects made more errors on the low frequency list. This conforms with prior results noted in the literature. The lack of significant difference for response latencies was contrary to prior findings. These results may have been due to a higher number of "no responses" on the low frequency list, and the quickness with which misperceptions of words were given. Only two subjects perseverated at all on either list. The low abstraction of the words and the lack of switching from one level of word difficulty to another were possible explanations for the results. Subjects were given the Boston Diagnostic Aphasia Examination and the Wide Range Achievement Test - Reading. The occurrence of perseveration on these tests was examined and classified. Two broad types of perseveration were noted (as well as 15 sub-categories). One type was of an intrusive nature whereby past responses interfered with or impinged on new responses, whether they be verbal or motor. The other was a form of modified responding which served an adaptive purpose. Correlations were calculated on the number of perseverative errors made on seven sub-tests of the Boston and the Wide Range Achievement Test - Reading. Significant positive correlations were found between three tests involving naming tasks. This was probably due to their similarity in nature. A significant negative correlation existed between the Wide Range Achievement Test - Reading and one of the naming tests. Perseveration tests have usually been found to have low positive correlations, sometimes reaching significance.