Twins’ lower IQ levels than single-born children not down to social factors
Social and economic circumstances do not explain why twins have significantly lower IQ in childhood than single-born children, according to a study in this week’s BMJ. Researchers studied 9,832 single-born children and 236 twins born in Aberdeen, Scotland between 1950 and 1956, using a previous child development survey as a base. They also gathered further information on mother’s age at delivery, birth weight, at what stage of the child’s gestation they were born, their father’s occupational social class, and information on other siblings.