Is it Cheating to Fantasize About Someone Else During Sex?

Our high school sex education teacher told us about a married woman who could only climax while imagining that she was being raped by Chinese communists. The teacher assured us this was perfectly normal. But is it really okay to fantasize about someone other than your significant other while making love — perhaps your partner’s best friend, an ex or that flirtatious neighbor? Or is it a form of infidelity?  Reply below