Quick! Tell me what order you are in the family and what that means to you. Were you the youngest, the baby, who was taken care of, protected (perhaps spoiled) and not left to make your own decisions? Were you the oldest, who had all the pressure and demands placed on you to “set an example?” Or were you a middle, or lost child, who kind of fell through the cracks? You weren’t really special on either end of the spectrum, were you? You may have even been the peacemaker as the middle child, trying to maintain the calm in a family that was otherwise a little chaotic.

Some experts believe that birth order is an important tool in shaping how you turn out as an adult. It determines how you see the world, how you expect the world to treat you, and how you treat others. If you are the baby, you will probably marry a firstborn. Why? Because they already know how to take care of you.

It’s not a conscious decision, this. It’s believed by some to be innate. Middle children may either marry the oldest or the youngest, for different reasons. For instance, the oldest again will know how to take care of you. The youngest will allow you to be the one who takes care of them. “Only” children have another problem. They are accustomed to being the center of attention (good or bad) and this may be hard to overcome later on in life.

Psychiatrist Alfred Adler (1870-1937) first proposed a theory on the effect of birth order on personality. (Personalities are the way that we deal with all the tasks of life, including our professions, friendships and even ways that we entertain ourselves). Adler said that the firstborn children are “dethroned” when the next child comes along and that they may never recover from that.

One must also consider the spacing between children, the demographics or social status, changes in the household over the years, and the number of children that grow up in that house. If there is a gap larger than 6 years, you’re looking at two different generations. For instance, if you have a sibling that is spaced at least that far apart from you, think about the different things that the two of you discovered growing up—different music, technology, even world events. If you are living in the United States, you have seen many different presidents, different problems, and different celebrities. It’s almost like you don’t have a lot in common, other than your family.

Family size also matters. If there are 12 children, the “middle child” can be any number of kids, or none of them. The youngest, depending on the years between children, may always be the baby, but the oldest one may change as gaps occur in the birthing.

Another theorist, Frank Sulloway, proposed that birth order has strong and consistent effects our personality traits. For instance, he wrote that the firstborns are more dominant, less open to new ideas, and more conscientious than later-born children. Another author, Delroy Paulhus and his colleagues have written that later-borns were more rebellious, open, and agreeable.

We believe birth order has such a profound effect because we see the same characteristics in the adult child as we saw when the child was young. This is not always true, however. Events such as a parent’s early death, a divorce or remarriage can profoundly affect a child’s development. The same holds true if a parent has mental health or substance abuse problems.

Other theorists disagree with the importance of birth order. Judith Rich Harris proposes that we may be affected by birth order within the family, but that it doesn’t have an effect on our personalities.

I will be writing more about these ideas in the near future. In the meantime, I invite you to share your own theories and experiences with us. There are lots of different families out there, and lots of different ways of growing up. We’re looking forward to hearing from you.