If you've ever intentionally smelled a partner's clothing for comfort, you've got a lot of company. Preserving, smelling and wearing the clothes of a sexual partner while separated is common, and it's probably normal behavior, suggests a University of Pittsburgh study.

Researchers who surveyed undergraduate students in long-term relationships found over half of men and nearly 90 percent of women had deliberately smelled their partner's shirt or blouse. A majority of women also report sleeping in or next to their partner's clothing.

Researchers Melanie L. Shoup and Sybil A. Streeter say the reason women have more interest in a partner's smell than men may hark back to evolutionary forces, possibly reflecting greater female choosiness in mate selection.

In discussing their data with colleagues, the researchers found anecdotal evidence for widespread "comfort smelling" within families, beyond the well-known scent bond that mothers have with their babies.

One man reported smelling his father's clothing when his dad was away, while one mother placed her own pajamas in her daughter's bed when the mom couldn't be there at bedtime. Many parenting guides even suggest leaving mom's shirt with baby in daycare.