A University of Chicago study on sexual behavior found sex does not decline as people age. One of the nation's most comprehensive studies of sexual behavior from early adulthood until late in life found sexuality remains an important part of life as people age.

The frequency of sexual activity, for those who are active, declines only slightly from the 50s to the early 70s.

In other research, Rick Thompson of Bowdoin College, in Brunswick, Maine, said the brain's chemistry affects how people attach to one another. Thompson, who teaches courses in hormones and behavior, social behavior and behavioral neuroscience, said that there is a chemical produced within the brain called oxytocin that promotes trust and attachment, and one of the things that promotes its release within the brain is sexual contact, particularly orgasm.

"Thus, the strengthening of attachments through sex or, more romantically, the deepening of love, may be a result of the actions of this brain chemical," Thompson said in a statement.