Oxytocin nudges distrustful men to invest 15% more in anonymous trust game

In 2005, a study led by University of Zurich economics professor Ernst Fehr demonstrated that intranasally administered oxytocin could increase trusting behavior in humans. However, subsequent research yielded conflicting results, leading to uncertainty about the hormone's effects on trust. To address this, an international team of researchers, including Fehr, conducted a new study involving 359 men with low trust disposition.

The men were randomly assigned to receive either oxytocin or a placebo before participating in a trust game under anonymous conditions. The study found that men who received oxytocin entrusted an average of 15% more money than those in the placebo group. When the data from this study was combined with results from a previous oxytocin study involving 578 low-trust men, the effect was found to increase trusting behavior by nearly 17%.

The researchers noted that this effect persisted even after controlling for personality traits. Fehr stated that the findings provide robust evidence of oxytocin's selective effect on trust, arguing against the idea that the hormone generally increases trust in all individuals. The exact biological mechanisms behind oxytocin's impact on trust remain unclear, and future studies are needed to investigate these mechanisms and determine whether the findings apply to women as well.