Hormone 'makes people trusting'

People can be made more trusting by manipulating parts of the brain that respond to a sense of betrayal, scientists have shown.

Researchers in Switzerland identified two brain regions that respond to being betrayed or cheated.

Suppressing their activity with the human brain chemical oxytocin made volunteers more trusting and less suspicious.

Oxytocin (OT) has been called the "love hormone". It appears to create emotional ties that bond lovers and mothers with their babies. Previous research had shown that oxytocin increased people's willingness to trust others.

The Swiss scientists asked volunteers to play two kinds of game, one based on trust and another on risk.

The study showed that in the trust game, but not the risk game, oxytocin reduced activity in two brain regions. One was the amygdala, which processes fear, danger, and risk of social betrayal. The other was an area of the striatum, part of the circuitry that guides behaviour based on feedback from rewards.

The findings showed that oxytocin affected responses specifically related to trust.

Dr Thomas Baumgartner, from the University of Zurich, and colleagues wrote in the journal Neuron: "If subjects face the non-social risks in the risk game, OT does not affect their behavioural responses to the feedback.

"In contrast, if subjects face social risks, such as in the trust game, subjects with OT demonstrate no change in their trusting behaviour although they were informed that their interaction partners did not honour their trust."

Psychologist Dr Mauricio Delgado, from Rutgers University in New Jersey, US, also writing in Neuron, said the research had "significant implications" for investigating social behavioural problems.

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