Costa PT, Jr., McCrae RR. On the need for longitudinal evidence and multiple measures in behavioral-genetic studies of adult personality. Behavioral and Brain Sciences 1987;10(1):22-23.

Suggests that psychologists' failure to use longitudinal methods to trace the course of development over the lifespan may explain their inability to understand the role of genetic factors and nonshared environment as sources of variances in children in the same family, as described by R. Plomin and D. Daniels.