A new study in the Journal of Marital and Family Therapy explored how men and women perceive online and offline sexual and emotional infidelity. Results show that men felt sexual infidelity was more upsetting and women felt emotional infidelity was more upsetting.

Monica T. Whitty and Laura-Lee Quigley of Queen's University Belfast surveyed 112 undergraduate students and asked them questions about sexual and emotional infidelity both offline and on the internet. 

When given the choice, men were more upset by sexual infidelity and women were more upset by emotional infidelity. 

Additionally, "men were more likely to believe that women have sex when in love and that women believe that men have sex even when they are not in love. It was not, however found that either men or women believe that having cybersex implied the other was also in love or that being in love online implied they were having cybersex."

"Given the newness of the internet, the rules have still not been clearly defined as to what are acceptable online encounters," the authors note. "Our results support a social-cognitive model as they demonstrate that social shifts have led men and women to think differently about sex and love."