If you are the parent of twins or triplets, you know that while your children share genes and a birthday, they don't share a personality. In fact, they are usually quite opposite! Why is this? To answer, we look to Alfred Adler's theory of personality development.
Adler was influenced by Darwin's study of genetic evolution and adaptation. He studied the finches of the Galapagos Islands. Darwin questioned why there was such a large variety of one species of finches on this one small island. Each variety had its own beak shape. Some beaks were suited for cracking nuts open, others had a beak suitable for eating seeds, others for plying off bark and eating insects.
Darwin concluded that the finches that first arrived on the island had quickly adapted in order to reduce the competition for the limited number of berries on the island. Adaptation of a beak to eat nuts reduces the competition for berry food and strengthened the possibility for finch survival.
The same phenomena can explain how children work to differentiate their personalities and take unique approaches to life in order to carve out their own niche in the family ecology and thus decrease competition by being non-comparable.
The more comparable the siblings the more they work to differentiate. Two of the biggest comparables are age and gender. Clearly twins and triplets are MORE comparable than serial born offspring, and children of the same gender are more comparable than a boy and a girl.
Children decide for themselves what role they will play in the family, parents reinforce those choices. What was your job in your family? Where you the responsible one, the clown, the sensitive one, the scholar, the athlete? Mr. Social, Ms. Patty Perfect? How have your multiples found ways to be unique in your family? Big eater or picky eater? Good sleeper or bad sleeper? Mild-mannered or wild temper? Tries and gives up or tenacious to the end?
Adler, a world-renowned psychologist, was brought in from Vienna to comment on the Dionne Quintuplets. Because of his poor English, it was misreported that he had advised to "separate the children." The media railed against this position. In fact what he said was that they should be "raised (treated) individually" as the unique individuals that they were.
Adler found common personality characteristics associated with birth order. He stated that the birth order itself (ordinal position) didn't "cause" these personality difference, but rather that each serial birth child is born into a different family environment. The child then must adapt and respond creatively in order to find his unique place or position in the family and thus reduce competition and secure survival.
Adler argued that the child is responsible (at a pre-conscious level) for creating the variations in personality that we see between siblings and likewise then, the similarities seen in people of the same birth order.
Let's have a quick look at how Adler's theory plays out in serial birth families.
So how do twins or triplets decide their roles?
You might think that if they are born together this theory must not apply. Actually, it serves to prove the point even more deeply since Adler's birth order is about "psychological order" rather than "numerical order" and therefore any child is free to select which role and attributes they will assume. This can be seen in families where the eldest child is sickly and takes on the role of the baby in the family, or the second child that sees that the first is struggling and not doing a good job of being the eldest decides to take on the role of "being the responsible/eldest."
With twins and triplets, they have to decide simultaneously how to differentiate and grab a position not taken by another. I had a mom of triplets tell me how when they walked to school one would race ahead, one would lag behind and the third would stay by her side. Each had their own way of approaching this simple task.
You may look at your own families and disagree, noticing that you have all scholars in your family, but look closer: does one take on reading while the other prefers mathematics? Or if you have an all hockey family, does one play goal the other a forward? Adler believed we are born with genes and a temperament, but that it didn't matter what cards you were dealt, it was how you decided to play your hand that mattered!