First-borns always knew it to be true, but now, they have research to back them up.

A new study published in the Journal of Human Resources has revealed that first-born children tend to be smarter than their younger siblings.

University of Edinburgh researchers believe this may have something to do with the fact that first-born children receive more mental stimulation from parents during their early formative years. 

The study gathered data from the U.S. Children of the National Longitudinal Survey of Youth, in which 5,000 children were monitored and assessed every two years until adolescence. The assessments spanned categories from reading to vocabulary to matching letters. Information about the children’s environmental factors, including family background and economic conditions, was also gathered.

As early as age one, the research found that first-borns excelled over their younger siblings. While younger siblings received the same emotional support as their older counterparts, it was revealed that parents tend to give first-born children more support when it comes to tasks that develop thinking skills, like reading, crafting and playing instruments. 

The researchers also found that mothers took more risks – like increased smoking – during pregnancies with second and third children.

The researchers say these findings might shed light on the “birth order effect”, wherein first-born children tend to make more money or get higher education than their younger siblings.

“Broad shifts in parental behavior are a plausible explanation for the observed birth order differences in education and labor market outcomes,” said study author Ana Nuevo-Chiquero of the University of Edinburgh School of Economics.

First-borns, try not to lord this information over your younger siblings too much; if you must, be sure to explain it very slowly.

h/t Paste Magazine