The differential effect of conation on intelligence test scores among brain-damaged and control subjects

Conation, or the ability to apply effective effort in completing a task over time, has been shown to be impaired in brain-damaged subjects. Various intelligence tests differ in the apparent extent to which they require conative ability. In this study we compared results earned by brain-damaged and control groups on three measures of intelligence: Wechsler Verbal IQ (VIQ), Wechsler Performance IQ (PIQ), and the Henmon-Nelson Test (HNT) of Mental Ability. Test scores were converted to T-score distributions for the combined groups in order to delete possible effects of differences in standardization procedures and the normative samples on which IQ scores were generated. The degree of impairment shown by the brain-damaged subjects was in direct relationship to the extent to which the three intelligence measures appear to require conation. The results support a generalization that intelligence tests that require a greater conative ability tend to produce lower scores for brain-damaged persons, as compared to controls, than do intelligence tests that are less demanding of conation.