Humans are among one of the few types of species that walk the Earth that pick a mate for life. Most different types of species, on the other hand, roam like free butterflies, from one mate to another throughout their lifetime.
Cheating is a taboo action that some people in relationships may choose to do on their own free will. It involves tarnishing the trust of your significant other to go off with someone else while the relationship is still very much in place.
Unfortunately, cheating continues to leave a strong footprint in today's society, but there's a logical scientific explanation behind why it happens, and it has to do with genetics and the brain.
As it turns out, Dopamine, a chemical the brain uses to make us feel good, plays a big role in cheating. Genes also play a role - in a study, 50% of participants with the long allele version of a gene related to cheating were found to have cheated on their partners, while only 22% of participants with the short allele version of that same gene were found to have cheated.
The cuddle hormone vasopressin is also thought to play a large role in cheating. When the trust and intimacy feeling wears off, we naturally wander to try and feel that hormone kick in again elsewhere. Those with lower levels of vasopressin are more likely to cheat on their significant other, while those with higher levels of vasopressin are more likely to stick with their partners.
There are also other factors, such as money, drugs, and sex life issues, which can lead to cheating, but they're far less scientific so we won't bore you with the details!