6) Saudino, K.J., & Cherny, S.S. (2001). Parental Ratings of Temperament in Twins. In R. Emde & J. Hewitt (Eds.), Infancy to Early Childhood: Genetic and Environmental Influences on Developmental Change (pp 73-88). Oxford University Press: New York, New York.

This chapter examines parental ratings of temperament on the Colorado Childhood Temperament Inventory (CCTI). Both parents rated children at ages 14, 20, 24 and 36 months on the CCTI. Researchers found that parents rated MZ twin resemblance as moderate, whereas DZ twins were often perceived as having opposite temperaments. This pattern of results did not emerge when temperament was assessed through observational measures. These results suggest that parental ratings, the most common method used to assess temperament in infancy and adulthood, are prone to contrast effects and bias.