The effect of stimulus presentation rate on syntax test performance in brain-injured adolescents

The purpose of this study was to explore how testing procedure influences performance after traumatic brain injury, and how this influence varies as a function of the subject's information-processing abilities. Twelve brain-injured subjects completed three versions of the Listening/Grammar subtest of the Test of Adolescent Language. In the first condition, sentences were presented at 2-s intervals, in the second at 4-s intervals, and in the third at variable intervals controlled by the subject. Scores in each condition were correlated with measures of working memory strorage and processing ability. Performance in the 2-s condition was significantly influenced by working memory processing ability, whereas performance in the 4-s condition was significantly influenced by working memory storage ability. Both aspects of working memory contributed to performance in the variable condition, although only processing was significant. As a group, subjects with better working memory processing ability preferred the variable interval condition, which allowed greater flexibility, while subjects with poor processing ability found it more difficult. The results are discussed in terms of clinical assessment and intervention.