A rather controversial area of psychological research is the role of pheromones on human behavior. A pheromone is a chemical substance produced and released into the environment by an animal affecting the behavior or physiology of others of its own species.  Although pheromones are known to play a significant role in signaling between members of the same species among animals to affect various behaviors, it is not clear that this is also true in humans.

Some psychologists have argued that pheromones may affect the menstrual cycle in groups of women and the olfactory recognition of a newborn by its mother. Some argue that individuals may exude different odors based on mood. Although there is some evidence, nothing is conclusive on whether or not humans have functional pheromones.

In animals, we see two types of pheromones. Primer pheromones that cause slow, long-term physiological changes, such as hormonal effects; and signaling pheromones that produce rapid behavioral effects, such as mating.  In humans, there is some evidence of primer pheromones. However, for all the published research that shows these effects, there is an equal number of studies showing that there are no effects. At this stage in the study of psychology, no human pheromone has yet been found.

Primer Pheromones:

• Definition: Primer pheromones are chemical signals that cause slow, long-term physiological changes in the recipient. These changes often involve alterations in hormonal levels or developmental processes rather than immediate behavioral responses.
• Effects:
  • Hormonal Changes: They can trigger significant hormonal shifts that affect reproductive cycles, growth, or other physiological processes. For example, in some animal species, primer pheromones can synchronize the menstrual cycles of female mammals living together. (PERIOD SYNC PRIMER HORMONES LOL)
  • Developmental Effects: These pheromones may influence developmental stages, such as puberty or maturation, by affecting endocrine systems.
  • Example: In rodents, certain primer pheromones can regulate the timing of puberty and reproductive readiness.

Signaling Pheromones:

• Definition: Signaling pheromones are chemical signals that induce rapid, often immediate behavioral responses from the recipient. These pheromones typically affect behaviors related to mating, territory marking, or social interactions.
• Effects:
  • Behavioral Responses: They trigger quick and observable changes in behavior, such as mating, aggression, or social bonding. For instance, signaling pheromones can attract mates during the breeding season or alert individuals to the presence of predators.
  • Communication: These pheromones often play a crucial role in social interactions and communication within a species, helping individuals convey information about their reproductive status, dominance, or social hierarchy.
  • Example: In insects, such as moths, signaling pheromones are used to attract mates over long distances, while in mammals, they can influence immediate social behaviors, such as forming bonds or avoiding conflicts.

Two potential human pheromones are Androstadienone (AND) – found in male semen and sweat – and Estratetraenol (EST), which is found in female urine, which Zhou Et Al investigated.

Pheromones and Aggression

Pheromones and aggression In the animal kingdom, animals will often attack members of their own species if they feel threatened. Males tend to do this to protect their territory and their mates. They will attack other males that invade their territory, but they will not attack other females or, in lab conditions, neutered males.

To definitively demonstrate that a pheromone exists, one must design a repeatable experiment, a bioassay, that shows that a smell molecule (odorant) causes a particular effect on the receiver. In this case, the effect would be an aggressive response. In order to test this in mice, Chamero et al (2007) attempted to isolate molecules found in mouse urine. They swabbed the backs of neutered male mice with various potential pheromone molecules and then introduced him as an intruder into the cage of a healthy male mouse. Using this technique, they were able to narrow it down to a protein that may be a pheromone that provokes aggressive behavior.

However, aggression in mice is very different from aggression in humans. Is there any chance that we also have an aggression-provoking pheromone?

How does one "smell" a pheromone? Pheromones seem to be detected by a structure called the vomeronasal organ, a tube at the base of the nasal cavity directly behind the nostrils that is filled with sensory neurons. It is found in most amphibians, reptiles, and nonprimate mammals, but is absent in birds and most primates. Surgical removal of the VNO eliminates territorial aggression and territorial marking in male mice and male hamsters.