The evidence is in

To my younger brother Larry and our younger sister Judy: Nyah, nyah, nyah.

Birth order within families has long sparked sibling rivalry, but it might also impact the child's personality and intelligence, a new study suggests. First-borns are typically smarter, while younger siblings get better grades and are more outgoing, the researchers say.

Larry, you're more outgoing than I am, right? Judy, you certainly got better grades. I rest my case.