There is a strange correspondence between the experimental test of Bell's theorem, verifying the most radical prediction of quantum theory, and phenomena observed with identical twins. Bell's theorem concerned measurements on two photons with a common origin that are subsequently allowed to separate widely. Bell predicted that if quantum mechanics held true, measurements on the two photons should show a correlation that is unexplainable in classical physics. This was indeed found; the results seem to require a mysterious, non-local linkage that crosses physical space without losing strength with distance and without delay in time. A similar effect seems to be true with identical twins separated in infancy and reared apart.

The study of identical twins separated shortly after birth and reared apart are the only human studies where the genetic component is constant while environmental components are variable. As expected, physical characteristics such as height, weight, and menstrual symptoms are found to be greatly alike among such twins. However there were surprises. In many cases these twins laughed alike, described symptoms in the same way, smoked a similar number of cigaretes, chose similar creative pursuits, and sometimes even married the same number of times. In addition, there was an inexplicable trail of similar names sometimes associated with such twins. For example, there were two adopted infants both named Jim by their adoptive parents. When they were reunited at age 39 they found their lives were marked by a trail of similar names. Both had dogs named Toy. Both married and divorced women named Linda and had second marriages with women named Betty. They named their sons James Allan and James Alan, respectively. Another pair of long separated twins, Bridget and Dorothy, named their sons Richard Andrew and Andrew Richard, respectively, and their daughters Catherine Louise and Karen Louise. In the case of Berta and Herta, the twins had the same nickname of "Pussy" yet the nicknames were in different languages since the twins lived on different continents and had not met since the age of four. Are all these "genetic" factors?