We are in an age of self-esteem, which is why only firstborns should read this article. It reports on new research that has found that the oldest child tends to be the smartest one in the family. Years ago, the Berkeley psychologist Frank Sulloway published a book on this politically incorrect subject, and the latest study just out of Norway corroborates his research.

In a way we are surprised to find out that eldest children are brighter. After all, siblings come out of the same gene pool and we might presume that they share pretty much the same upbringing and social environment. Still, the facts are that even children close in age raised in the same household are very different in many respects. One respect is that firstborns tend to be Numero Uno when it comes to brains. As a firstborn myself, I find this reassuring.

Eldest children seem to have IQs that are, on average, three points greater than those of the next smartest sibling. For second, third and fourth-borns who will no doubt write to inform me that they happen to be the smartest in their family, the term "average" means that this is a general trend and does not apply to every situation. By way of analogy, men are taller than women and it is no refutation of this general observation to point out that Eleanor is five feet eleven inches and Fred is 4 feet six.

While the new Norweigian study focused on males, the sample size was extremely large. All 18 year-olds in Norway must register for the military and take IQ tests, providing researchers with really good data to evaluate the effects of birth order. Moreover, the study's conclusions support numerous other studies conducted on men and women in several other countries. Sulloway's book Born to Rebel summarizes this evidence.

It's important to realize that the 2.3 point IQ difference between firstborns and second-borns is quite significant. Sulloway points out that it gives firstborns a 13 percent greater chance of getting into a good college. It's equivalent to an extra 45 points on the SAT test, which can make all the difference for an admissions committee.

The interesting question is why firstborns tend to be smarter. The main reason seems to be that firstborns get their parents' undivided attention, while subsequent children have to compete for mom and dad's time. This fact also has psychological consequences: firstborns tend to be conservative and believe in the system. Second and third children are typically more rebellious and also in some ways more creative. So when you run into guys like Michael Moore--creative but not very smart--ask if they are second, third or fourth in their family.

While firstborns tend to be smarter than second-borns, and second-borns tend to be smarter than third-borns, the differences diminish with each subsequent child and quickly become negligible. That's probably because the firstborn has the great advantage of the undivided attention of the parents, not to mention more "adult" conversation in the home, while subsequent children must fight for parental attention and the home atmosphere can easily become "dumbed down" with everyone making goo-goo noises for the benefit of the youngest child.

Some critics have pointed out that other factors--such as the death of a parent, or the presence of grandparents in the home--can also affect the IQ distribution in the household. This is certainly true, but it only means that birth order is not the only factor. What everyone seems to agree on is that middle children get the least parental attention. Dalton Conley, author of The Pecking Order, says that while middle children don't necessarily have the lowest IQs, they are "25 percent less likely to be sent to a private school...and they're five times more likely to be held back a grade."

To the old adage, "Choose your parents carefully," I must add a corollary, "Choose your date of conception wisely."