If twins are raised in different households, are they more or less likely to be similar to one another, compared to twins raised in the same household? The answer might surprise you.

In a study about mothers’ child-rearing attitudes toward their children, researchers found that mothers of identical twins had a greater tendency than mothers of fraternal twins to dress their children alike. Dressing one’s twins alike is understandable – it can be hard for a parent to resist the positive attention she receives from the passers-by who marvel at the delight of two same-aged siblings wearing the same adorable outfit.

But oh, how a twin child wants to be different from her co-twin!

In her book The Sister Knot: Why We Fight, Why We’re Jealous, and Why We’ll Love Each Other No Matter What, Dr. Terri Apter explains that siblings typically strive to distinguish themselves from one another so that they can gain new attention from their parents. It’s easier, after all, to win the competition for parental love when you are only competing against yourself. When children grow up together in the same family, however, they need to be viewed as distinct and separate from the other children. Dr. Apter highlights the fact that identical twins who were raised apart are more likely to be similar to each other than those who were raised in the same household. “Growing up together,” she notes, “[and] identifying with one another, [are] a good way to ensure differences.”

So maybe not all hope is lost when a parent dresses her twins alike — her children may make a concerted effort to self-distinguish. And if those efforts yield the desired results, those twins will be more distinct from one another than if they were raised separately and had simply allowed nature to take course.