Maternal preference between premature twins up to age four.

This paper describes methods of measuring a preference a mother develops for one twin over the other and describes the effect such preference has on the intellectual functioning and behavior of 24 twin pairs over 4 years. Results indicate that the majority of mothers develops a preference for one premature twin within 2 weeks after birth and maintains this preference for at least 4 years. The preferred twin has fewer behavior problems and a higher IQ at age 4. However, temperament is not correlated with preferential status.