The science of love takes on a new twist on why men stray. According to a study, that cheatin' heart is really about brain chemistry. And for better or for worse, some scientists say, men are born with it.
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.
Dr. Brenda Wade has written three books on marriage and relationships.
She 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 makes them less likely to be married and more likely to have bad relationships.
"I say to men who have problems with cheating number one you must answer the question: Where did you learn cheating behavior," Dr. Wade said.
But it can also be 'unlearned.'
Gene or no gene, 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 our selves who we want to be," Dr. Wade said.
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.