Identical twins are intriguing, but most people cannot tell you why this is so. I have thought a great deal about this over the years that I have studied twins in my lab, interviewed them in their home or met them on the street. I think I may have one answer: We live in a world that appreciates and expects individual differences in appearance and in behavior. So when we encounter two highly matched individuals, this experience challenges our beliefs about the way that the world works. The likenesses of identical twins trigger a variety of reactions, both positive and negative, yet everyone is drawn in. Some people may even feel jealous
of the social closeness most identical twins experience and celebrate. Of course, identical twins are never exactly alike, and some differ in profound ways, such as in disease susceptibility or in gender identity
. These cases are truly extraordinary. I also want to make a case for fraternals who are often overlooked by the media, yet are warmly welcomed in scientific laboratories. There are many variations among fraternal twins—some have different fathers, some are conceived weeks apart and some look like they come from different ethnicities. We can learn a great deal about human behavior and development by taking a closer look at these multiples. Many topics can be explored in the singular world of twins. And they are not just interesting or entertaining (they are!), but they also offer a take on who we are and how we got there. I look forward to sharing my thoughts and experiences with twins, now and in the future.