1.2.2 Influence of Pheromones on Behavior

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Key Definitions

Pheromone: chemical messenger that communicates information (like fertility or sexual attractiveness) from one member of a species to another

Putative human pheromone: chemical substance that is hypothesized to be a human pheromone like androstadienone (AND) and estratetraenol (EST)

Essential Understanding

→ Pheromones are chemical messengers that communicate info form one member of a species to another

↳ processed in the accessory olfactory bulb in animals, but it’s unclear whether or not there exists a biological mechanism to process pheromones in humans

→ search for human pheromones has taken the form of both laboratory and field experiments

→ Lundstorm and Olsson (2005): experimental procedure that showed that AND increased the mood of female participants if the study was carried out by a male, but not a female experimenter

↳ suggests that AND can modulate women’s emotional reaction to men, indicating its possible function as a human pheromone

→ Hare et al (2017): carefully designed experimental procedure demonstrated that neither AND nor EST could signal gender or attractiveness

↳ since these are the basic functions a human pheromone must be able to perform, these results bring into question the status of these chemicals as putative human pheromones

→ In field experiment Cutler, Friedman, and McCoy (1998), researcher showed that a synthetic human pheromone applied to aftershave cream increased the attractiveness of men and women, which resulted in a higher incidence of sexual behaviors

↳these studies, however, only serve as examples of laboratory and field experiments in this area

→ it can concluded that for the time being that research has been contradictory and inconclusive, and that the human pheromone has not been found

Biology of Pheromones

→Pheromones are chemicals that signal information from one member of a species to another

↳ while detectable in animals, their role in humans is undetectable

→ Pheromones are chemical messengers

↳ known chemicals that provide chemical communication between members of the same species, like neurotransmitters and hormones

↳however, unlike the other chemical messengers, pheromones communicate from one species member to another

Ex: female fertility: pheromones have been shown to play an important role in the sexual behavior of a number of species like many mammals

→ Where in the brain are pheromones processed?

↳ mammals have a structure called vomeronasal organ (VNO) located in the nasal cavity

↳ this structure is connected through nerves to the brain region called the accessory olfactory bulb, an area adjacent but separate to the main olfactory bulb, brain area responsible for processing regular smells

→ Processing pheromonal information in the human brain

↳ human fetuses have the accessory olfactory bulb, but it regresses and disappears after birth

→ for the VNO, some people have it and some don’t

↳ for people with it, it appears to be disconnected form the nervous system, but there’s a possibility that pheromonal info in humans is processed elsewhere

→ Androstadienone and estratetraenol: Two chemicals that have been extensively studied as putative human pheromones

Researches

• Lundstorm and Olsson (2005): effects of AND on women’s attraction to men

  ↳ key: being exposed to AND increases the mood of women in the presence of a male experimenter, suggesting that this chemical may trigger attraction

Aim: investigate the effect of AND on the mood of women in the presence of men

Participants: 37 heterosexual women, mean age 25 years with a normal menstrual cycle

Method: experiment; 2 × 2 experimental design (two independent variables with two levels each)

Procedure:

→ female participants’ mood was studied in a 2 × 2 experimental design

→ were then assessed after being exposed to either AND or a control solution, and in the presence of a male or female experimenter

→ experimenter carried out a number of measurements including several questionnaires→ one of them measured participants’ mood

↳ either female (age 28) or male (age 30)

Results:

↳ AND increased women’s mood in the presence of a male experimenter, but not in a female experimenter

Conclusion:

↳ AND may serve the function of signaling sexual attractiveness, supporting the role as a pheromone

• Hare et al (2017)→ the ability of AND and EST to signal gender and attractiveness

  ↳ key: any chemical that is hypothesized to be a human pheromone signaling sexual attractiveness must be able perform two functions:

  → I. signal gender

  → II. affect perceived attractiveness of the faces of the opposite sex

  ↳ showed that neither AND or EST performed either functions, which brings into question their status as human pheromones

Aim: investigate if AND and EST signal gender and affect mate perception

Participants: 140 heterosexual adults

Method: experiment; repeated measure design

Procedure:

→ participants completed two computer-based tasks on 2 consecutive days

↳ on one of the days they were exposed to the putative pheromone (AND or EST) masked with clove oil

↳ on the other day they were exposed to the control scent (clove oil alone)

→ order of the conditions was counterbalanced

↳ first task: participants were shown five “gender-neutral facial morphs” and had to indicate the gender (male/female)

↳second task: shown photographs of individuals of the opposite sex and asked to rate their attractiveness on a scale form 1 to 10

Results:

→ there was no difference in gender assigned to the morphed faces in the pheromone vs. control condition

→ no difference in average attractiveness ratings of the photographs of the opposite sex

Conclusion:

→ the two chemicals (AND or EST) don’t acts as signals of gender or of attractiveness

↳ based on this result, researchers concluded that these chemicals don’t qualify as human pheromones

• Cutler, Friedman, and McCoy (1998)→ a field experiment with a synthetic human pheromone

  ↳ key: researcher showed that a synthetic human pheromone applied to a man’s aftershave lotion increased the incidence that seemed to suggest sexual contact by women

  ↳ from this, they concluded that pheromones may increase sexual attractiveness of men to women

Aim: investigate if a synthesized human pheromone can increases sociosexual behavior of men

Participants: male volunteers→ all heterosexual, 25-42 years old, in good health with regular appearance

Method: field experiment; independent measures design

Procedure:

→ each participant was asked to use his regular aftershave lotion after every shave for the duration of the study

↳ also given a behavioral calendar that they had fill out on a daily basis, indicting the incidence of the following six behaviors on that day:

→ petting, affection, and./or kissing

→ sleeping next to a romantic partner

→ sexual intercourse

→ informal dates

→ formal dates

→ masturbation

→ given a baseline period of 2 weeks

→ after the 2 weeks, a technician added either ethanol or a synthesized pheromone with ethanol to their aftershave lotion (depending on condition)

↳ ethanol was used as a masking agent to compensate for the possible smell of the pheromone

→ then followed by six more weeks of using aftershave regularly and filling out the behavioral calendar

Results:

↳ compared to the control group, many participants in the pheromone group had an increase over the baseline in the first 4 behaviors

→ differences were not observed in the last two behaviors

Conclusion:

→ researchers took this result as evidence that the synthetic human pheromone applied to the aftershave lotion increased sexual attractiveness of men and women

↳ an alternative explanation would be to day that it was the men’s own libido that increased (so that they initiated contact with women more often)

↳ however, the fact that there was no change in the last two behaviors contradicts this explanation

→ Spontaneous sexual encounters were affected, indicating that the contact might have been initiated by women

Criticism of Human Pheromone Research

→ research in the area of human pheromones has produced contradictory findings

↳ much of the research is flawed by the fact that authors are commercially interested in the results

↳ also has a number of methodological limitations compromising the quality of a typical study

→ Inconclusive Research

↳ must be admitted that research is inconclusive

↳ existence of human pheromones is not a scientifically established fact

→ Contradictory Findings

↳ some studies support the existence of human pheromones (i.e. Lundstrom and Olsson (2005))

↳ some studies oppose the existence of human pheromones (i.e. Hare et al (2017))

→ field studies in this area are rarely conducted due to the effort and funding it requires

↳ when conducted, their done by companies who are financially interested in results (i.e. Cutler, Friedman, and McCoy (1998)→ author of the first study was the founder of a company that produced and market a synthetic human pheromone)

↳ they also don’t release the formula of the chemical in their research paper

→ thus, an independent researcher can’t try and replicate the studies’ results

→ Inherent Methodological Limitations

↳ major methodological limitations inherent in any research study of this field (i.e. Verhaeghe, Gheysen, Enzlin (2013))

→ Commercial Interest