18) McGuire, S., & Roch-Levecq, A. (2001). Mother’s Perception of Differential Treatment of Infant Twins. In R. Emde & J. Hewitt (Eds.), Infancy to Early Childhood: Genetic and Environmental Influences on Developmental Change (pp 247-256). Oxford University Press: New York, New York.

Mothers of twins were interviewed about the amount of discipline, affection and attention they displayed toward one twin compared to the other. In this study data was obtained from 176 mothers who were interviewed when their same-sex twins were 14,20,24 and 36 months of age. Researchers found that mother’s reports differed significantly depending on whether the twins were identical or fraternal. The majority of mothers of identical twins treated the pair the same, whereas only 1/3 or the mothers of fraternal twins reported treating the twins similarly. These results suggest that mothers are reacting to genetic differences among infant twins, and that genetically influenced infant behaviors, such as temperament, play a role in early parenting.