Birth Order Experts
In 1958 Professor Robert F. Winch at Northwestern University published a book entitled Mate Selection in which he suggested that complementary relationships work best. In essence, this is the theory that opposites attract. He found, for example, that dominant people prefer submissive partners, and maternal people like dependent partners (New York: Harper, p. 332).

German psychologist Walter Toman's research indicated that Winch was right and that opposites do attract, but Toman went further and suggested that birth order could be used to find out which people would be most compatible. His book Family Constellation is the basis of much of the pop psychology approach to compatibility.
In 1996 Frank Sulloway revealed that during times of social revolution, opposites actually don't attract, they oppose one another. This finding, published in Born to Rebel, suggests that a firstborn and a lastborn (like Brad Pitt and Angelina Jolie) may run into relationship problems, especially during times of social upheaval.
More recently, William Cane looked at all the research on birth order and compatibility. He found that Winch and Toman's idea that opposites attract is fundamentally valid, although individuals need to keep in mind that philosophical and temperamental conflicts may erupt between those of opposite birth orders, especially during social revolutions. Cane's findings appear in The Birth Order Book of Love. (Photo: Brad Pitt and Angelina Jolie on a motorcycle in Ho Chi Minh City, Vietnam. Copyright © 2006 Reuters.)