Deceitful and despicable is one description that wronged wives could apply to their cheating husbands.
Plain stupid is another. For scientists have concluded that men who sleep around are likely to have lower IQs.
Dr Satoshi Kanazawa, an evolutionary psychologist from the London School of Economics and Political Science, said the smarter a man is, the less likely he is to cheat on his partner.
His theory is based on the assertion that through evolutionary history, men have always been "mildly polygamous".
That has changed today, however, and Dr Kanazawa explained that entering a sexually exclusive relationship is an "evolutionarily novel" development for them.
According to his theory, intelligent people are more likely to adopt what in evolutionary terms are new practices--to become "more evolved".
Therefore, in the case of fidelity, men who cannot adapt and end up succumbing to temptation and cheating are likely to be more stupid.
"The theory predicts that more intelligent men are more likely to value sexual exclusivity than less intelligent men," he explained.
According to his theory, the link between fidelity and intelligence does not apply to women because they have always been expected to be faithful to one mate--even in polygamous societies.
Dr Kanazawa's research, in the journal Social Psychology Quarterly, also claims that intelligent people are less likely to believe in God or hold conservative views.
Analysing the American National Longitudinal Study of Adolescent Health, he found young adults who regarded themselves as 'very liberal' had an average IQ of 106, while those who saw themselves as "very conservative" had an average IQ of 95.
According to Dr Kanazawa, that is down to people who are smarter being more open to new ideas. Those who are less intelligent cling to belief in God, a relic of our evolutionary past, he added.
"So, more intelligent children are likely to grow up to go against their natural evolutionary tendency to believe in God and they become atheists."