Reproducible research into human chemical communication by cues and pheromones: learning from psychology's renaissance

Despite the lack of evidence that the ‘putative human pheromones' androstadienone and estratetraenol ever were pheromones, almost 60 studies have claimed ‘significant' results. These are quite possibly false positives and can be best seen as potential examples of the ‘reproducibility crisis', sadly common in the rest of the life and biomedical sciences, which has many instances of whole fields based on false positives. Experiments on the effects of olfactory cues on human behaviour are also at risk of false positives because they look for subtle effects but use small sample sizes. Research on human chemical communication, much of it falling within psychology, would benefit from vigorously adopting the proposals made by psychologists to enable better, more reliable science, with an emphasis on enhancing reproducibility. A key change is the adoption of study pre-registration and/or Registered Reports which will also reduce publication bias. As we are mammals, and chemical communication is important to other mammals, it is likely that chemical cues are important in our behaviour and that humans may have pheromones, but new approaches will be needed to reliably demonstrate them. This article is part of the Theo Murphy meeting issue ‘Olfactory communication in humans’.

Reproducible research into human semiochemical cues and pheromones: learning from psychology’s renaissance

As with other mammals, smell in the form of semiochemicals is likely to influence the behaviour of humans, as olfactory cues to emotions, health, and mate choice. A subset of semiochemicals, pheromones, chemical signals within a species, have been identified in many mammal species. As mammals, we may have pheromones too. Sadly, the story of molecules claimed to be ‘putative human pheromones’ is a classic example of bad science carried out by good scientists. Much of human semiochemicals research including work on ‘human pheromones’ and olfactory cues comes within the field of psychology. Thus, the research is highly likely to be affected by the ‘reproducibility crisis’ in psychology and other life sciences. Psychology researchers have responded with proposals to enable better, more reliable science, with an emphasis on enhancing reproducibility. A key change is the adoption of study pre-registration which will also reduce publication bias. Human semiochemicals research would benefit from adopting these proposals.

Reproducible research into human semiochemical cues and pheromones: learning from psychology’s renaissance

As with other mammals, smell in the form of semiochemicals is likely to influence the behaviour of humans, as olfactory cues to emotions, health, and mate choice. A subset of semiochemicals, pheromones, chemical signals within a species, have been identified in many mammal species. As mammals, we may have pheromones too. Sadly, the story of molecules claimed to be ‘putative human pheromones’ is a classic example of bad science carried out by good scientists. Much of human semiochemicals research including work on ‘human pheromones’ and olfactory cues comes within the field of psychology. Thus, the research is highly likely to be affected by the ‘reproducibility crisis’ in psychology and other life sciences. Psychology researchers have responded with proposals to enable better, more reliable science, with an emphasis on enhancing reproducibility. A key change is the adoption of study pre-registration which will also reduce publication bias. Human semiochemicals research would benefit from adopting these proposals.

A Scientific Basis for Humanae Vitae and Natural Law

This article will review Humanae Vitae’s predictions of the effect of oral contraceptives (the pill) on male–female relationships and societal behaviors. A scientific, biochemical basis underpinning these predictions is made. Evidence of human pheromones will be given. Evidence for the changes in male and female pheromones caused by the pill is given. Observational and experimental evidence of changes in primate and human behaviors by pheromones is detailed. The role these changes have caused in attractiveness and selection of mate by both males and females in preferences concerning major histocompatibility genes is examined. These changes have also resulted in societal changes in sexual behavior and family structure and have led to increased violence against women. Biochemical evidence for the abortifacient properties of the pill is given. The use of natural family planning is given as a needed alternative to the harms of the pill. Summary: The human biological bases of Humanae Vitae’s predictions of the effect of the pill on male–female relationships are examined. Evidence of the presence of pheromones in primates and humans is given. The pill changes human pheromones, odors which are subconsciously detected. These pheromones cause humans to change what they find attractive in a mate. Choosing a mate while on the pill can result in unstable and more violent unions. The biological basis for the fact that the pill causes abortion of human embryos is given. A healthy alternative for fertility control is explained.

Putative sex-specific human pheromones do not affect gender perception, attractiveness ratings or unfaithfulness judgements of opposite sex faces

Debate continues over the existence of human sex pheromones. Two substances, androstadienone (AND) and estratetraenol (EST), were recently reported to signal male and female gender, respectively, potentially qualifying them as human sex pheromones. If AND and EST truly signal gender, then they should affect reproductively relevant behaviours such as mate perception. To test this hypothesis, heterosexual, Caucasian human participants completed two computer-based tasks twice, on two consecutive days, exposed to a control scent on one day and a putative pheromone (AND or EST) on the other. In the first task, 46 participants (24 male, 22 female) indicated the gender (male or female) of five gender-neutral facial morphs. Exposure to AND or EST had no effect on gender perception. In the second task, 94 participants (43 male, 51 female) rated photographs of opposite-sex faces for attractiveness and probable sexual unfaithfulness. Exposure to the putative pheromones had no effect on either attractiveness or unfaithfulness ratings. These results are consistent with those of other experimental studies and reviews that suggest AND and EST are unlikely to be human pheromones. The double-blind nature of the current study lends increased support to this conclusion. If human sex pheromones affect our judgements of gender, attractiveness or unfaithfulness from faces, they are unlikely to be AND or EST.