Laws of Attraction: Scientists Find Out How People Choose Sexual Partners

Saliva, smell and symmetry are the key characteristics of a new scientific study.

Scientists have discovered new factors that help explain why we are sexually attracted to some people more than others.

Sexual attraction is caused by several signals at the unconscious level, which play a decisive role in arousing our sexual interest for certain people, a new study published by Psychology Today said.

According to the research, the first thing that attracts individuals to each other is body and facial symmetry. People can consciously sense when a person's face is symmetrical and prefer to have her or him as a sexual partner because a symmetrical body is perceived as a sign of "good" genes.

Moreover, people choose their partners based on smell. According to the research, the human brain is capable of analyzing the smell of another person and can determine if the potential partner is ill. It can also reveal character traits of an individual, the study says.

Another important cue is the chemical composition of the saliva. While kissing, one's brain tests how much the immune system of a potential sexual partner is different from his or her own.

The bigger the difference, the greater the chance that their future children will be more resistant to diseases.