In 2007, researchers from the University of Texas categorized 237 motivations for humans to have sex. Recently, researchers at the University of Toronto divided the most common into two broad categories: approach motives pursue a positive outcome, like increasing intimacy; avoidance motives aim to avoid conflict or guilt. The Canadian team found that adding the fairly un-sexy drives of duty, resignation and guilt which significantly affect the health of a relationship, and could spell the difference between a happy marriage and a rocky one. Elizabeth Bernstein is a columnist for the Wall Street Journal, where she wrote about the studies published by University of Toronto in October.
Identifying The Motivation To Have Sex

Jean KOULEV via flickr Creative Commons