Quiz: Does Birth Order Affect Who You Are?

A first-born or only child may be more likely to become a doctor or lawyer. Younger siblings more often turn to the arts or the outdoors. In part, you can credit parenting.

Parents may over-protect oldests or onlies. So they tend to follow more brain-based interests. When later children show up, parents can be more relaxed and hands-off.

All seven of the original Mercury astronauts were firstborns. Other famous firstborn trail-blazers: Winston Churchill, Hillary Rodham Clinton, and Oprah Winfrey.

It’s lonely at the top -- or at least, at the beginning! A 2007 survey of corporate leaders found that 43% of CEOs were firstborns, 33% were middle children, and 23% were youngest children.

A younger brother is more likely to put on the pads -- or go ski jumping, sky diving, motorcycle racing, or play lacrosse -- than his older brother.

A study that looked at birth order and "dangerous" sports in college students found that firstborn men were more likely to avoid those sports. Younger brothers were more daredevil.

Even when parents try to be even-steven, it rarely works out that way. Kids born first get as much as 3,000 more hours of quality time with parents than younger siblings do at the same age.

Parents spend about equal time with two or more kids. But there's less total free time than there was when a firstborn passed through a given age.

Older moms say they feel closest to their "babies" no matter what the family size or spacing between kids.

In the same study, mothers said firstborns were the ones they'd turn to when facing personal problems or a crisis.

Firsborns tend to try to be "perfect" more often than later-borns. But kids without siblings, who are often treated like little adults, seem to have even more of this trait.

It's clear why birth order interests us so much. Most of us weren't born as the only child in a family.

Kids who are spaced less than two years apart often have more conflict than those born more than two years apart, pediatricians say. 

Doctors often tell new parents there's no such thing as a dumb question. Parents climb a steep learning curve about how to take care of a child.

That's why studies show that they call the doctor more with a firstborn. But time builds confidence. Parents also figure out which problems a doctor can help with and which they can handle on their own.