He says the results suggest that females identify more strongly with their image and appearance, and use Facebook as a platform to compete for attention.

Stefanone describes the study results in a video interview: http://www.youtube.com/watch?v=T1GQHoLyS5Q&feature=relmfu.

"The results suggest persistent differences in the behavior of men and women that result from a cultural focus on female image and appearance," he says.

The study, "Contingencies of Self-Worth and Social-Networking-Site Behavior," was co-authored by Derek Lackaff, PhD, University of Texas, Austin, and Devan Rosen, PhD, University of Hawaii, Manoa. It appeared in the journal's current issue.

Its purpose was to investigate variables that explain specific online behavior on social network sites. Among other things, the team looked at the amount of time subjects spent managing profiles, the number of photos they shared, the size of their online networks and how promiscuous they were in terms of "friending" behavior.

In the study, 311 participants with an average age of 23.3 years -- 49.8 percent of whom were female -- completed a questionnaire measuring their contingencies of self worth. The subjects were also queried as to their typical behaviors on Facebook.

"Those whose self esteem is based on public-based contingencies (defined here as others' approval, physical appearance and outdoing others in competition) were more involved in online photo sharing, and those whose self-worth is most contingent on appearance have a higher intensity of online photo sharing," Stefanone says.

Stefanone notes that the women in this study who base their self worth on appearance were also are the most prolific photo sharers.

"Participants whose self worth is based on private-based contingencies (defined in this study as academic competence, family love and support, and being a virtuous or moral person)," says Stefanone, "spend less time online." For these people, social media are less about attention seeking behavior.