Human Pheromones: Abandoned by the Wayside

The great intellectual wagon train of behavioral science rolls on, leaving behind heaps of junk that the scientific pioneers no longer find useful. Miles back there’s a big pile of specialized “instincts” for this and “drives” for that. Further up, the trail is strewn with Skinner boxes and the shabby wreckage of behaviorism. In the near distance are items more recently jettisoned: the excess baggage of mammalian pheromones.

Georgia State researcher Aras Petrulis is the latest to toss the pheromone concept to the side of the road. In a review article to appear soon in the journal Hormones and Behavior, he examines “chemosignals, hormones and mammalian reproduction.” His conclusions echo those of Richard Doty.

Petrulis doesn’t deny the importance of smell. In his view, “it is clear that social odors play a substantial and oftentimes obligatory role in mammalian reproduction.” However, he believes that the actions of these social odors rarely meet the definition of a pheromone. Why?

The role of learning and memory in the behavioral and physiological responses to opposite-sex conspecifics is generally under-appreciated by the non-specialist. [Don’t be offended, FN readers! Dr. Petrulis’s condescension is directed toward other PhDs—those outside his narrow discipline.] Many of the reproductive effects reviewed above are clearly subject to learning in adulthood as evidenced by their dependency on sexual experience or prior contact with chemosignals as well as by their ability to be conditioned to previously neutral odors.

This dependence on learning and context undercuts the most fundamental idea of a pheromone; that is, that responses to it are “instinctual” and therefore not learned. Similarly, the fact that most chemosignals altering mammalian behavior and/or physiology are complex mixtures often lacking species-specificity, rather than being potent and essential singular compounds, further erodes the utility of the term “pheromone”. Because of these concerns, it is perhaps wise to restrict the term to molecules that have met each and every criterion of a pheromone, as used in the classical ethological sense.[Emphasis mine.]

And if we restrict the term as he so gingerly suggests, where does that leave us with respect to human pheromones?

Lastly, it should be clear that chemosignals are neither necessary nor sufficient for human reproduction nor do they have a privileged place in directing human social behavior. Positive findings of human chemical communication, when not based on flawed analysis . . . are often inconsistent, and at best, demonstrate modest effects on human behavior and physiology.

So take it from a guy who studies sex behavior for living: drop the human pheromones and lighten your load.

The study discussed here is “Chemosignals, hormones and mammalian reproduction,” by Aras Petrulis, published online in Hormones and Behavior, March 29, 2013.