In addition to having the privilege of being the first to use clothes and toys, first born children can now add another advantage over their siblings to the list.

According to a study published in the Journal of Human Resources, first born children may have better thinking skills than their siblings because they received more mental stimulation during their early stages of development.

Researchers from the University of Edinburgh, the Analysis Group, and the University of Sydney found that children who were born first typically scored higher on IQ tests than their younger siblings.

For the study, researchers used data from the U.S. Children of the National Longitudinal Survey of Youth on nearly 5,000 children who were monitored from pre-birth to 14. Every two years, the children in the longitudinal survey were assessed on a slew of categories including tests on reading, vocabulary assessment and matching letters.

The research found that first-born children typically perform better than their siblings as early as age one, and that may be in part due to changes in how parents treat subsequent children. According to the study, parents were less likely to partake in mentally stimulating activities with their younger children, meaning they may not have developed the same thinking skills as their older sibling.

“Our results suggests that broad shifts in parental behavior are a plausible explanation for the observed birth order differences in education and labor market outcomes,” Ana Nuevo-Chiquero, of the University of Edinburgh School of Economics, said in a statement.