A new research has confirmed what many parents long suspected: Second-born kids are more likely to be rebellious in later life than their more conservative older siblings.
According to scientists, who published their study in the journal Child Development, firstborn children are likely to conform while younger siblings are prone to more independent personalities, reports The Telegraph.
To reach the conclusion, researchers at the Pennsylvania State University, the University of Hawaii at Manoa and Purdue University interviewed 364 children in the United States between the ages of seven and 19 and their parents.
They also took saliva samples to measure testosterone levels and asked the children to keep a diary of their activities outside school.
A spokesman for the researchers told the Daily Mail: "Second-born children showed increases in traits like adventurousness and independence across adolescence, whereas in firstborns, these traits did not change much over time.
"These findings are consistent with the idea that firstborns conform more, while second-borns are more likely to rebel."
The study found that girls who spent time with other gals developed more feminine characteristics while boys became more masculine if they played with other boys. But, both boys and girls appeared to benefit from having female friends, becoming more adventurous and independent if they played with girls.
Another key finding was, children who showed faster rates of increase in the hormone testosterone in early adolescence were not as affected by social influences on their personality development.