The way we think is determined by the 'struggle for life' of our distant Stone Age ancestors some million years ago. As a result, husband and wife are jealous in different ways. She finds it more difficult when he has an emotional relationship with someone else than when he cheats. With him it is just the other way around: he condones a crush, but he cannot stand it when she does it with someone else.
Statement
A man is more likely to accept it when his partner falls in love with someone else than a woman.