The French say “je ne sais quoi” (literally, "I don’t know what") when describing a certain mysterious something that makes a particular person sexually attractive.
You’d think that with something as vital to the survival of the species as sexual selection, we’d all be very conscious of the cues we (and prospective sex partners) use for mate selection.
But as the French saying suggests, we are often not consciously aware of these cues. Numerous laboratory studies (where young adults rate the attractiveness of photos of members of the opposite sex, or smell clothes worn by test subjects of the opposite sex) have proven that although we know whom we prefer as prospective mates, we don't always know the exact reasons why we prefer them.
After reviewing a list of subliminal "come hither" stimuli that might shed some light on the mystery of physical attraction, I'll explain how--if you're so inclined-- you can take advantage of the new information.
Unconscious sexual cues
Based on recent research, here is a list of unconscious attractors, indicating which attributes unconsciously arouse our interest, along with which sensory modalities are thought to be responsible for communicating signals of sexual attractiveness.
Body and face symmetry (from smell alone) We can consciously sense when someone’s face is symmetrical. Women also unconsciously prefer scents (on t-shirts) of men who have symmetrical body and facial features (signs of health and genetic fitness). Exactly what the chemical signals of symmetry are is unclear.
Personality (from smell and visual cues) T-shirt sniff tests also indicate that we have a limited ability to determine which of the “Big 5” personality (e.g. Extraversion and Neuroticism) traits are dominant in another person from unconscious olfactory cues (again, scientists don’t yet know which chemicals are responsible). Apparently, we can also glean similar information unconsciously just by watching video clips of people’s behavior.
Illness (from smell) Putting aside obvious cues, such as the odor of infected wounds, new evidence suggests we can unconsciously detect olfactory cues associated with bacterial infection in another person. Both humans and animals tend to avoid mates that are ill.
Genetic diversity (from smell and taste) There is evidence that humans can sense, from both sweat and saliva, how close a match another person’s DNA is to their own by detecting major histocompatibility complexes (MHCs). In order to avoid mutations in offspring and stillbirths, mating with someone whose DNA (as evidenced by MHC’s) is very different from one’s own is a good idea. Also, combining your genes with someone with very different immune characteristics increases the odds your children will have robust immune systems. In my last blog, I speculated that people kiss on the lips because disproportionately large swaths of sensory and motor brain tissue respond to lip, tongue, and mouth stimulation. But some biologists now believe that we kiss on the mouth in order to “taste” the saliva of prospective partners for compatible MHC’s.
Non-familiarity (from both smell and visual cues) Research from kibbutz communities in Israel and colonies in Taiwan, where non-relatives are raised in close proximity, shows that humans prefer to mate with those who were not raised with them (mating rates among non-relatives who grew up together is very low). Again, low rates of mate-pairing among adults who grew up together may foster healthy genetic diversity. At least from the point of view of mate selection, familiarity really does breed contempt!
Similar personality (from smell) In a research article, "Birds of a feather do flock together," Wu YouYou and colleagues at Cambridge found that we are drawn to people—both as mates and as friends—who share our personality traits. Whether or not we are conscious of being attracted to people because they have similar personalities is unclear, especially in light the research just cited on “sniffing out” the Big 5 personality traits.