75. Schmitz, S., Fulker, D.W., Plomin, R., Zahn-Waxler, C., Emde, R.N., & DeFries, J.C. (1999). Temperament and problem behavior during early childhood. International Journal of Behavioral Development, 23, 333-355.

At ages 14, 20, 24, and 36 months, mothers of twins completed the Colorado Childhood Temperament Inventory. At age four, problem behavior was assessed using maternal reports on the Child Behavior Checklist. The temperament trait of Emotionality at all four prior age points correlated significantly with the CBCL Total Problem Score at four years as well as with the broadband groupings of Internalizing and Externalizing. In addition, Shyness at all four ages correlated significantly with the broadband grouping of Internalizing. Longitudinal behavior genetic analyses indicated that these phenotypic predictions from early temperament to later behavior problems are largely due to genetic factors.