According to a study published in the Proceedings of the National Academy of Sciences (PNAS), intranasally administered oxytocin selectively increases trusting behavior in men with a low disposition to trust, boosting financial amounts entrusted to strangers by roughly 15% to 17% compared to a placebo group. Led by researchers from the University of Zurich, Otto von Guericke University Magdeburg, and the University of Antwerp, the findings help resolve a two-decade scientific dispute over the hormone’s social effects.
Two Decades of Debate Over Oxytocin and Trust
Back in 2005, a scientific paper published in the journal Nature came from an investigation directed by Ernst Fehr, an economics professor at the University of Zurich. That initial project provided the first evidence that intranasally administered oxytocin—a natural hormone and neurotransmitter influencing social interactions—could increase trusting behavior in humans. Yet, according to myscience.ch coverage of the new research, subsequent studies failed to deliver a uniform picture. Some laboratories corroborated the finding, while others detected no general effect whatsoever.
Critics frequently pointed out that earlier investigations relied on small sample sizes, suffered from post-hoc hypothesizing, and utilized methodologies that made cross-study comparisons difficult. Because of these inconsistencies, the scientific community remained divided on whether and under what conditions the hormone actually altered trust. The PNAS study, published in August 2026, sought to clear up this confusion by testing a predefined hypothesis on a much larger cohort.
Methodology and Findings of the PNAS Study
To test the hormone’s true impact, researchers Ernst Fehr of the University of Zurich, Bodo Vogt and Paul Bengart of Otto von Guericke University Magdeburg, and Carolyn Declerck of the University of Antwerp recruited 359 men. According to the study data, every participant was rated as having a low disposition to trust based on a preliminary questionnaire. The team deliberately confined the participant pool to men to ensure direct comparability with older oxytocin trials.
Did you know? The study subjects were split randomly to receive either oxytocin or a placebo before participating in a strictly anonymous trust game, where they decided how much money to hand over to an unknown person.
Participants characterized by a skeptical baseline who were administered oxytocin shared roughly 15% more funds with their partners on average compared to the control participants given a placebo. Furthermore, when the team pooled this data with a comparable earlier study, the broader analysis of 578 low-trust men revealed an increase of nearly 17% in trusting behavior. Fehr noted in the myscience.ch report that the effect remained intact even after controlling for various personality traits.
Selective Effects and Unanswered Biological Questions
The new data explicitly rejects the theory that oxytocin makes all people universally trustful. Instead, the hormone acts selectively on individuals who already lean toward skepticism. Interestingly, within the low-trust demographic, the exact baseline score did not change the outcome; men with exceptionally low trust scores reacted similarly to those with moderately low scores.
Despite these clear behavioral metrics, the underlying biological mechanisms remain a mystery. The study did not directly investigate cellular or neurological pathways. However, Fehr suggested that the hormone might intensify expectations of cooperation or lessen the fear of being cheated. Additional research is planned to examine these mechanisms and determine whether the trust-boosting trend applies to women as well.
Frequently Asked Questions
What does oxytocin do to trust levels?
According to PNAS research, oxytocin selectively increases trusting behavior in men with a low disposition to trust, boosting financial risk-taking in trust games by roughly 15% to 17%.
Does oxytocin make everyone more trusting?
No. The data shows the hormone does not create a general trust-boosting effect across the entire population; it specifically targets individuals who possess a low baseline disposition to trust.
Who led the recent 2026 study?
The research was conducted by an international team including Ernst Fehr from the University of Zurich, Bodo Vogt and Paul Bengart from Otto von Guericke University Magdeburg, and Carolyn Declerck from the University of Antwerp.
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