(NBC) - Some say love, happiness and loyalty are the secrets for the happily-ever-after, but no matter the vows, some scientists say cheating is in the genes.
"There's a gene that's been shown that if men have this particular gene or a variant of the gene, they have more trouble in relationships," said Dr. Brenda Wade, a marriage and relationship expert.
Wade, who has written three books on marriage and relationships, agrees with a study done in Sweden, in which scientists studied the gene types of 552 sets of twins. They found a bonding chemical in some men that makes them less likely to be married and more likely to have bad relationships.
"I say to men who have problems with cheating, 'No. 1 you must answer the question: Where did you learn cheating behavior,'" Wade said.
But it can also be 'unlearned.' The study also found that the brain can be trained to resist temptation.
"The key is recognizing the unlimited potential that we have to make ourselves who we want to be," Wade explained.
Scientists say men don't have to cheat, but they do have to work harder at staying faithful.
As for women, the scientists will put them under the monogamous microscope next.