When the cuddle hormone turns nasty – oxytocin linked with violent intentions

For many years, the hormone oxytocin was caricatured as the source of all human goodness – trust, altruism, love, and morality. Among the findings that contributed to this picture were the discovery that sniffing oxytocin increases people's trust and generosity in financial games; that it aids face recognition; and that its release is associated with maternal bonding; and with orgasm.

However, the picture has grown a lot more complicated of late, with findings showing that oxytocin has a "dark side" – for example, boosting envy and shadenfreude. Now a team of researchers led by Nathan DeWall has further sullied the reputation of this once idolised molecule. They've demonstrated that for certain people in particular circumstances, exposure to oxytocin might actually lead to increased violence.

The researchers split 93 undergraduates (47 men) into two groups – one group sniffed oxytocin, the other group sniffed a salt water solution. The students didn't know whether they'd received the oxytocin or the placebo, and the researchers were also blinded to who'd received what. Next the students completed two tasks designed to make them stressed, including giving a public presentation to an unfriendly audience. Finally, they answered two questions about their tendency to be physically aggressive, and further questions about how likely it was that they'd engage in violence towards a current or former romantic partner based on how they currently felt.

Here's the main finding – oxytocin boosted the self-confessed likelihood of being violent towards a partner, specifically in those students who admitted that they have a proclivity for physical aggression. DeWall's team think this fits with an emerging, more nuanced understanding of oxytocin's effects. It remains true that the hormone plays an important role in maintaining human relationships, but this isn't always an innocent function. Previous research shows oxytocin can increase intolerance and aggression towards outsiders. Now we learn that for people who typically resort to aggression to keep hold of their romantic partners, stress plus increased oxytocin nudges them towards violence.

"Our findings add to the understanding of the 'prickly side of oxytocin'," said DeWall and his team. "Far from being a panacea for all social ills, oxytocin may have a much more diversified effect, as in the current case."

Further reading

DeWall, C., Gillath, O., Pressman, S., Black, L., Bartz, J., Moskovitz, J., & Stetler, D. (2014). When the Love Hormone Leads to Violence: Oxytocin Increases Intimate Partner Violence Inclinations Among High Trait Aggressive People Social Psychological and Personality Science, 5 (6), 691-697 DOI: 10.1177/1948550613516876