Economists at the University of Edinburgh have concluded that first-borns have a higher IQ test score than their siblings as early as age one. The findings, published in the Journal of Human Resources, could help explain the so-called birth order effect when older siblings in a family enjoy better wages and more education in later life, according to researchers.

Almost 5,000 children were observed from pre-birth to 14 years old on their family backgroundand economic conditions. Every two years they were assessed on skills including reading and picture vocabulary.

Researchers also analyzed how parental behavior such as smoking and drinking during pregnancy was related to their child's test score. It was found that mothers took "higher risks" during the pregnancy of latter-born children.

Parents also offered less mental stimulation to younger siblings and took part in fewer activities such as reading, crafts and playing musical instruments. The findings showed that advantages enjoyed by first born siblings start from just after birth to three years of age. Parents changed their behavior as subsequent children were born.

WESTON, Phoebe. Disponível em: <http://www.dailymail.co.uk/home/search.html?>.Acesso em: mar.2017.