Sniffing the human body volatile hexadecanal blocks aggression in men but triggers aggression in women
Authors: Lior Gorodisky
Tatsuya Uebi
Daniel Amir
Liron Rozenkrantz
Eva Mishor
Aharon Ravia
Shiri Karagach
Noam Sobel
Edna Furman-Haran
Mamiko Ozaki
Ethan Livne
Kobi Snitz
Reut Weissgross
Timna Soroka
Danielle Honigstein
Rotem Zirler
Shani Agron
Aharon Weissbrod
Yaara Endevelt-Shapira
Tali Weiss
Joerg Strotmann
Netta Reshef
Diyala Karawani
Heinz Breer
Journal: Science Advances (2021)
Discipline: Multidisciplinary
Keywords: body volatiles; conspecific aggression; hexadecanal; human aggression; behavioral paradigms
Affiliations: Azrieli National Center for Brain Imaging and Research, Weizmann Institute of Science, Rehovot, Israel., Institute of Physiology, University of Hohenheim, Stuttgart, Germany., Department of Biology, Graduate School of Science, Kobe University, Kobe, Japan.

Abstract:  In terrestrial mammals, body volatiles can effectively trigger or block conspecific aggression. Here, we tested whether hexadecanal (HEX), a human body volatile implicated as a mammalian-wide social chemosignal, affects human aggression. Using validated behavioral paradigms, we observed a marked dissociation: Sniffing HEX blocked aggression in men but triggered aggression in women. Next, using functional brain imaging, we uncovered a pattern of brain activity mirroring behavior: In both men and women, HEX increased activity in the left angular gyrus, an area implicated in perception of social cues. HEX then modulated functional connectivity between the angular gyrus and a brain network implicated in social appraisal (temporal pole) and aggressive execution (amygdala and orbitofrontal cortex) in a sex-dependent manner consistent with behavior: increasing connectivity in men but decreasing connectivity in women. These findings implicate sex-specific social chemosignaling at the mechanistic heart of human aggressive behavior. 

Retracted: No

PubPeer comments:
 This article was reviewed on the error bar podcast episode 22: https: theerrorbar.com ?e=22 story 92: https: theerrorbar.com ?s=92. The review was done in the light of newspaper headlines about the article. The slightly-edited transcript is copied here: headline: MEN: SMELL POO TO RELAX tweet: making men women smell a chemical found in mice, on skin in poo makes men a bit less aggressive women a bit more aggressive in deliberately-annoying computer games. no one but the authors or journalists seems to know why. description: the online science platform Science.com, the journal Science the Daily Mail all lead with the news that the smell of babies makes men less aggressive women more aggressive. you d expect, then, that the reported study involved men women smelling babies. it didn t. what the researchers actually did was use a synthetic organic molecule called hexadecanal, or HEX, in liquid form. HEX was first found to be emitted by mice. by mice. but there are similar-looking chemicals in humans which may, as in mice, play a role in social interaction. HEX is found in human skin, faeces, breath saliva. the researchers asked 127 people to sniff HEX or an inert control smell, then to play some aggression-rousing computer games with virtual opponents. the scientists measured how much the players chose to punish their annoying virtual opponents. after sniffing HEX men decreased their punishments, while women increased them. some more people were put into a brain scanner where sniffing the HEX chemical provoked more activity in the angular gyrus - an important part of the brain involved in language, social signals, movement, tool use, sniffing babies heads lots more. males females showed different patterns of brain activity connecting with the angular gyrus. these connections were interpreted in terms of the social significance of the annoying computer game. some extra data collected at another laboratory, showed that babies excrete HEX from their heads. this amazing finding confirms that babies are, in fact, human. the discovery that babies are human led the authors to propose an astonishing hypothesis: the smell of HEX makes men LESS aggressive so that they don t kill babies. the smell of HEX makes women MORE aggressive so that they can defend babies from (male) attack. yeah, that sounds fine. evaluation: do babies heads make men calm down? no. this paper has nothing to do with babies heads. remember: the natural version of the synthetic chemical is found in mice, many other animals in human skin, breath, saliva faeces. yes: faeces. maybe smelling poo calms men down? we may never know. having dealt with the baby red herring the nonsense, sexist, post-hoc, just-so story about why men constantly need to be stopped from killing babies, let s look at the data. along with the aggression findings, the men in the study also found the smell stimulus less intense than women, these ratings became more extreme as the experiment progressed. this finding could partly explain the aggression ratings, assuming that intense smells make people aggressive. but apart from that, i am ashamed to admit that i did not find anything so wrong in this paper. if you can get past the ridiculous confirmation-biased evolutionary-psychology bullshit that men want to kill babies women protect them - which i can t - then this seems a fair study. large sample sizes, clear presentation of methods data, sensible-sounding analyses, mostly good stats. indeed, this paper is so acceptable that it really winds me up. i can just see the red mist coming down over my eyes, the blood boiling in my veins all i can think about is going out to kill some babies. wait, here s my old pants. [deep breath in]... ahh, it really works. short conclusion: anything mammal will do ,