TO WHAT EXTENT DO PHEROMONES INFLUENCE HUMAN BEHAVIOR

TO WHAT EXTENT DO PHEROMONES INFLUENCE HUMAN BEHAVIOR?

PHEROMONES • The word pheromone is derived from the Greek words phero (I carry) and hormone (stimulating), so pheromones are chemicals that ”carry stimulation”. • Term appeared when scientists observed termites and noticed that a chemical substance released by one termite affects the behavior of other termites. • It was suggested as an umbrella term for various forms of chemical communication among members of the same species • For some social insects, chemical communication is the main form of communication. • Pheromones have also been shown to play a role in the behavior of mammals, mainly in mating behavior. • Ex. If he cannot sense pheromones signaling fertility, a male rhesus monkey will ignore the romantic attention of a female (Herz, 2009) • SO DO PHEROMONES PLAY A ROLE IN HUMAN BEHAVIOR? ? ? • It’s a subject of much debate

LOCALIZATION OF PROCESSING PHEROMONAL INFORMATION IN THE BRAIN • Although many pheromones have a smell, pheromonal information in the brains of animals is not processed in the same brain region as ordinary smells. • The main olfactory bulb is the region of the brain responsible for processing smell • Mammals have a separate structure called the vomeronasal organ (VNO) which is located in the anterior nasal cavity. • Nerves from the VNO in animal brains connect to a special region called the accessory olfactory bulb (this region is adjacent to, but separate from, the main olfactory bulb). • A major difficulty with extrapolating animal research to human behavior is linked to the fact that humans do not have either the VNO or the accessory olfactory bulb. • To be precise, human fetuses do have the accessory olfactory bulb, but it regresses and disappears after birth. • Some people do have VNO, while some do not • Even in those who have the VNO, it appears to be non-functional as there is no connection to the CNS • IF PHEROMONAL INFORMATION IS INDEED PROCESSED IN THE HUMAN BRAIN, IT MUST BE PROCESSED SOMEWHERE ELSE.

SEARCH FOR A HUMAN SEX PHEROMONE: LAB EXPERIMENTS • Evidence for the influence of pheromones on human behavior has been inconclusive. • There are many intriguing findings, but there is always an alternative explanation or lack of clarity that prevents us from claiming pheromonal effects with certainty • Lundstrom and Olsson (2005) • Aim: to study the effects of androstadienone – a derivative of testosterone and one of the chemical components of sweat. • Methods: • Studied a woman’s mood after being exposed to either androstadienone or control solution; and in the presence of either a male or female experimenter. • Results: • Androstadienone increased women’s mood in the presence of a male experimenter and had no effect when the experimenter was female. • It is tempting to conclude that androstadienone as a pheromone intensifies women’s reactions to men, but the study has important limitations: • The concentration of androstadienone used in the study was much higher that the normal amount found in male sweat which is a common feature of pheromone studies • It is hard to separate the effects of the pheromone from the effects of the experimenter. • For example, what if the male experimenter was simply particularly handsome?

SEARCH FOR A HUMAN SEX PHEROMONE: LAB EXPERIMENTS • It is widely recognized that a basic function of a sex pheromone, whatever other additional functions it performs, is to signal gender. • If a chemical does not perform gender-signaling function, the chances are that it will not produce any other genderrelated effects and so it is not a sex pheromone. Therefore, one needs to show that it signals gender to call it a sex pheromone. • Hare et al (2017) • Aim: to investigate whether androstadienone (AND) and estratetraenol (EST)– the best-known candidates for human sex pheromones —signal gender and affect mate perception. • Methods: • The experiment used a repeated measures design. • Heterosexual participants completed two computer-based tasks twice on two consecutive days. • While completing the task, on one of the days they were exposed to the putative pheromone (AND and EST) masked with clove oil, and on the other days they were exposed to a control scent (clove oil only). • Substances were administered by a cotton ball taped under the nose throughout the task • The design was counterbalanced (some participants had the pheromone on the first day and the control substance on the second day, some vice versa). • The first computer-based task involved showing the participants five “gender-neutral facial morphs”, and participants had to indicate the gender (male or female). • In the second task participants were shown opposite-sex photographs and asked to rate them for attractiveness on a scale from 110

SEARCH FOR A HUMAN SEX PHEROMONE: LAB EXPERIMENTS • Results of Hare et al (2017): • Results of the first task revealed no difference in gender assigned to the morphed faces in the pheromone versus the control condition. • Similarly, results of the second task revealed no difference in the average attractiveness ratings of opposite-sex photographs. • Researchers concluded that AND and EST do not act as signals of gender or of attractiveness, which means that they do not qualify as sex pheromones. • So far, we have two contradictory studies– but they are not as contradictory as it seems. • We may admit that some chemicals such as AND influence women’s mood. However, these chemicals do not signal gender and they do not affect mate perception, so we cannot classify them as a sex pheromone. • MAYBE THE PROBLEM IS IN THE ARTIFICIALITY OF THE EXPERIMENTAL TASKS…?

SEARCH FOR A HUMAN SEX PHEROMONE: FIELD EXPERIMENTS • Cutler, Friedmann and Mc. Coy (1998) • Aim: to investigate whether synthesized male pheromones increase sociosexual behavior of men. • Methods • Participants (38 men) were recruited through local press releases that invited volunteers to participate in an experiment with the aim to “test whether a male pheromone added to aftershave lotion would increase the romance in their lives” • Selection criteria: • Male, heterosexual, 25 -42 years old, good health, not taking meds, regular appearance (not too handsome nor unattractive), shaving regularly, and having adequate social skills with women • Participants were screened with personality questionnaires and anyone too strongly deviating from the average was excluded • Participants were randomly divided into two groups (in a double-blind manner) • Each participant brought his aftershave lotion and was asked to use it after every shave (minimum three times a week throughout experiment) • Participants were also given a behavioral calendar which they had to fill out daily indicating the incidence of six behaviors on that day: • Petting, affection and/or kissing • Sleeping next to a romantic partner • Sexual intercourse • Informal dates (dates not arranged) • Formal dates (pre-arranged dates) • Masturbation • After a baseline period of two weeks, subjects returned to the laboratory and the technician (who was blinded to the conditions) added either ethanol or pheromone with ethanol to their aftershave lotion. • The pheromone was a synthesized version of a pheromone naturally secreted by men • Participants went on to use their aftershave lotion for a six-week trial period (so total study time was eight weeks)

RESULTS OF CUTLER, FRIEDMANN AND MCCOY (1998) • There were significantly more men in the pheromone group who had an increase over the baseline in the first four behaviors. • Ex. 47% of men in the pheromone condition reported an increase in the frequency of sexual intercourse, as compared to 9. 5% in the placebo group • Differences were not observed for the last two behaviors. • Why? • Researchers concluded that applying the synthetic pheromone resulted in an increase of sociosexual behaviors “in which the willingness of a female partner plays the major role”. • They took it as evidence that the synthetic human pheromone actually increased the attractiveness of men to women.

CRITICISM OF RESEARCH INTO HUMAN PHEROMONES • Population validity: the fact that most studies used self-selected samples (volunteers who respond to posters or ads) • Participation bias: in most studies, researchers try to not disclose the true nature of the study, however, there are hints that may lead participants to guess the true aims of the study…ex. The study surveys or interviews include questions about participants’ sexual orientation • Ecological validity: studies typically use a concentration solution of the pheromone much higher than that found in natural sweat • Internal validity: other smells can act as a confounding variable • Experimenter bias: the looks and behavior of the experimenter or the research assistant conducting the experiment is difficult to keep constant • Ethics: for example, in one study women were required to wipe pads containing armpit sweat (obtained from donors) under their noses each day for three months • Researchers who conduct human pheromone studies are often commercially interested in the results. So it is a possibility that publication bias occurs. - they might only publish supporting evidence and not the “unsuccessful” research.