I read some psychology research where they asked a large cohort of women to keep a diary of the private fantasies, what they masturbate to, etc. These were rated in terms of the degree of infidelity. Independent of that, their husbands were rated on a masculinity score. The two scores inverse-correlated fairly well, so that wives of low-masculine husbands fantasised more about cheating. This may explain why some guys are subject to cuckolding repeatedly. Women judge masculinity through many modes, eg the pitch of his voice, his height, his brow-ridge / chin, musculature, dick size, hand size, attitude, etc.