Conley explains in his book that a lot of other factors affect the behavior of first-borns and last-borns much more strongly. "Early death of a parent, timing of economic shocks to the family, gender expectations and roles in the family, you name it," Conley said, "outside influences, random events — birth order is basically at the bottom of that list."
"It's just like astrology," he added. "When you see a good fit, you say, 'Hah! He's such a Gemini.' When you see a good fit, you say, 'hah, he's such a first-born, aggressive control freak,' but when it doesn't fit the mold you don't even notice it."
Conley says Sulloway's data is quite selective, relying on cases that support his claims and ignoring those that don't. When I asked him about that, Sulloway said, "It is human nature that we look for evidence to confirm our theories. But I took rather unusual steps in born to rebel to minimize as much as possible that sort of bias."
Sulloway does acknowledge that there may not be hard and fast rules about birth order. "Humans are complex," he said, "The fact that you can find things that are more important than say, birth order, doesn't mean that birth order isn't something we don't learn from."
While some researchers say Sulloway is right, others are skeptical. But, there is at least one point on which both sides agree: middle children get the worst deal.
According to Conley, middle children are "25 percent less likely to be sent to a private school than they were before, and they're five times more likely to be held back a grade."
Ellen Cowan agrees that being in the middle "stinks." Her older brother gets a better deal because he's going to be first at everything, like prom and graduation and college, she says. And her younger brother, well, he's in a better spot, because he'll get to be the last in the family to go through these milestones. She even said "there's no point" to being a middle child.
Both her brothers agreed. Neither of them said they'd change spots with her.
Ellen's mother sensed that Ellen needed something more and she's trying to make it up to her, partly by doing something with Ellen every week. It's a good idea, say many experts, for parents to do this with any middle child.
Conley said middle children need "time where they're not being compared, at least in their own heads, to their older, or to their younger siblings. Time where they can get the individual attention from their parents."
So while the claims about first-borns and last-borns may not hold up. Parents should be sure to take care of the middle child.
Sibling rivalry and the constant bickering and fighting that it sparks can drive parents crazy. It's so common, but is there any way to turn brawling brothers into buddies?
Jeff and Alex Franco know all about the frustrations of dealing with sibling rivalry. Their sons, 8-year-old Spencer and 6-year-old Jackson, were constantly at each other's throats. The Francos just couldn't understand why their boys can't get get along, and allowed us to videotape some of the boys' ineractions. "We thought they would be best friends," their mom, Alex, said.