Intelligence and the Prediction of Academic Achievement in Closed-Head Injured Adolescents and Young Adults

The present study examined the relationship between intellectual, other neuropsychological variables and academic achievement in a sample of closed-head injured adolescents and young adults (N = 61). Specifically, severity of injury, crystallized ability and fluid ability were examined as to their prediction of academic achievement. Severity of injury was measured as length of post-traumatic amnesia. Crystallized ability was measured as the average of WAIS-R Information, Vocabulary and Comprehension subtests (age corrected standard scores). Fluid ability was measured as the average of WAIS-R Picture Completion, Block Design, and Object Assembly subtests (age corrected standard scores). Three mediation models are described examining the importance of crystallized and fluid variables in mediating between severity of injury and academic achievement. Crystallized ability was found to be a significant mediator as determined by a significant change in beta between the unmediated effect of PTA on achievement ([beta] = -.287; SE = .005, p < .05) and the mediated effect ([beta] = -.031; SE = .004, p > .1. Fluid ability was also found to be a significant mediator as determined by a significant change in beta between the unmediated effect of PTA on achievement ([beta] = -.287; SE = .005, p < .05) and the mediated effect ([beta] = -.034; SE = .004, p > .1. The difference score between crystallized and fluid variables failed the criteria to be considered as a significant mediator between severity of injury and academic achievement. Implications for these findings are discussed.