Birth order may set personality types in motion, but they remain in motion for a lifetime. The granddaddy of birth-order psychology, Alfred Adler, was clear in his assertion that we are continually influenced by changes in our family and the world at large.
"The myth people want to believe about birth order is that you have to be a certain way based on order, but reality is never that stagnant," says Jack Agati, M.A., an expert on the influence of families. "Adler's idea was that it's a dynamic, ongoing process that sets up how you interact with the people around you. The feedback that you get helps you develop some of the skills, talents and characteristics that you get from a birth order."
Consider the brothers in "The Godfather." First-born Sonny Corleone wanted to emulate his father and inherit control of the family, but he was a hot-headed risk taker. Fredo should have been next in line for the power seat, but he was sickly and dimwitted ("I can handle things! I'm smaht!"). With Fredo being too frail and Sonny all shot full of holes, mild-mannered Michael—the third-born—was the only candidate fit to wear his father's ring. Only Mario Puzo saw that coming.
Only children are similar to first-borns, but have their unique traits
The increasing number of "onlys" stands to impact the way we negotiate personal and business relationships in our culture, Agati asserts. One reason is that onlys tend to develop relationships very, very gradually. "Their loyalty is beautiful. But if you violate that friendship, you’ll never get it back."
People without siblings tend to have rich inner lives, in part because their imagination has long been a way of entertaining themselves. Their creativity is also encouraged and sustained. Agati cites the example of an only child's picture hanging on the fridge. "There's no sibling to replace it or tear it down," he says. "Who's going to criticize it? By the time parents take it down, they can frame it and give it to the...