A relative latecomer to academia (he received his Ph.D. at 32), Hebb had worked as a schoolteacher, farmer, and laborer before embracing psychology. He is perhaps the most eclectic of the group of differential psychologists gracing this site, having a profound interest in many of the 'big questions'. A long association with Lashley and a stint with Herrick primed Hebb's interest in the relationship between nature and nurture. Best known for the Organization of Behavior, Hebb's study of the effect of early and late brain damage on intelligence has had a major impact on the psychology of individual differences. Importantly, Hebb's research (presented at the 1941 Annual General Meeting of the American Psychological Association) provided independent, neuropsychological support for a multifaceted intellectual structure. Coincidentally, Raymond B. Cattell introduced the theory of fluid and crystallized intelligence at this same forum. Did you know? Hebb's work with primates led to his anthropomorphic description of "chimpanzee horror." This is when these animals are confronted with replicas of dismembered body parts.