Oxytocin Increases Trust in Men with Low Baseline Trust, Study Finds

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Intranasal oxytocin increases trusting behavior in men who have a low natural disposition to trust, according to a high-powered study published in August 2026 in the journal Proceedings of the National Academy of Sciences (PNAS).

High-Powered Trust Experiment Design and Methodology

For two decades, scientific claims regarding oxytocin and human trust faced skepticism due to underpowered sample sizes, inconsistent replication results, and analytical practices like hypothesizing after results are known. To resolve this debate, the PNAS study recruited 359 men who scored low in dispositional trust. According to the PNAS paper, the experiment achieved 95% power to detect a positive effect.

Participants took part in an anonymous trust game where they decided how much monetary value to send to an unknown partner. Researchers administered intranasal oxytocin to the subjects prior to the interaction. The experimental setup controlled for baseline personality traits and isolated the neurobiological variable to determine its precise causal impact on cooperative economic choices.

Quantifying the Oxytocin Trust Increase

Data analysis revealed that oxytocin administration boosted trusting behavior by roughly 15% among the low-trust participants. Furthermore, a pooled data analysis incorporating a previous sample of 219 low-trusting individuals produced a statistically significant 16.9% increase in trust.

According to the study authors, the results showed consistent effects across regression models that included controls for personality traits as well as models without those controls. Notably, researchers found no interaction effect between the hormone and the exact degree of dispositional trust within that low-trust group. This indicates that oxytocin’s trust-enhancing effect operates uniformly across individuals who share a low baseline level of trust.

The findings mark a shift from earlier assumptions that oxytocin universally increases prosocial behavior across all human populations. Instead, the data supports a selective model where the neuropeptide primarily alters behavior when an individual’s baseline trust is initially low, providing a clearer neurobiological picture of how the hormone influences human social interactions.

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