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Do you think it is the oxytocin? Keystone

Scientists from Zurich University have demonstrated how a squirt of the hormone oxytocin up the nose stimulates trusting behaviour in humans.

This content was published on June 2, 2005 - 19:46

The research, in this week’s edition of Nature, could lead to a better understanding of mental problems associated with social dysfunctions such as phobias and autism.

"Of course, this finding could be misused," said Ernst Fehr, the senior researcher in the study, thus anticipating most people’s first reactions and consequent plans to make their millions.

"Some may worry about the prospect that political operators will generously spray the crowd with oxytocin at rallies of their candidates," said Iowa University neurologist Antonio Damasio, who reviewed the experiments for the science journal.

"But those with such fears should note that current marketing techniques – for political and other products – may well exert their effects through the natural release of molecules such as oxytocin in response to well-crafted stimuli."

Other scientists say the new research raises important questions about oxytocin’s potential as a therapy for conditions like autism, in which trust is diminished.

Or perhaps the hormone’s activity could be reduced to treat rarer diseases such as Williams syndrome, in which children approach strangers fearlessly.

"Might their high level of trust be due to excessive oxytocin release?" asked Damasio. "Little is known about the neurobiology of trust, although the phenomenon is beginning to attract attention."

Markus Heinrichs, one of the co-authors of the study, believes that "a combination of effective psychotherapy methods with synergising oxytocin administration might have clinical benefits for the treatment of mental disorders".

Chemical bond

Oxytocin is secreted in brain tissue and synthesised by the hypothalamus. This small region of the brain controls biological reactions such as hunger, thirst and body temperature, as well as visceral fight-or-flight reactions associated with basic emotions such as fear and anger.

In humans and animals, this chemical messenger stimulates uterine contractions in labour and induces milk production. Indeed, it has already been suggested that an oxytocin nose spray may be a useful adjunct to stimulate breastfeeding.

Elevated concentrations of the hormone were also found in cerebrospinal fluid during and after birth, and experiments showed it was involved in the biochemistry of attachment – sheep and rat females given oxytocin after giving birth do not exhibit typical maternal behaviour such as grooming towards newborns.

Levels of oxytocin are also found to be higher among people who claim to be falling in love. It is also thought to mediate other forms of pair bonding such as friendship and family relationships. Reduction of sociophobic behaviour has been shown after treatment with oxytocin.

Oxytocin also plays some role in orgasms for both sexes. In males, oxytocin is said to facilitate sperm transport in ejaculation.

Trust fun

Scientists have recently wondered whether oxytocin is generally involved with other aspects of bonding behaviour – and specifically whether it stimulates trust.

In their experiments, the Swiss researchers tried to manipulate people’s trust by adding more oxytocin to their brains.

They used a synthetic version in a nasal spray that was absorbed by mucous membranes and crossed the blood-brain barrier. Researchers say the dose was harmless and altered oxytocin levels only temporarily.

A total of 178 healthy male students from universities in Zurich took part in a series of games of risk and trust.

The players were given notional currency and could choose to place all of it, some of it or nothing in the hands of trustees who would then decide how much to hand back after the stake had been tripled.

Some players were given a whiff of oxytocin; some inhaled a vial of air. None of the players knew what they were sniffing and none knew whether the trustees were trustworthy or not.

Brain studies

Those who got a noseful of oxytocin showed a greater propensity to trust someone than those who simply inhaled air.

But when the trustee was replaced with a computer, both sets of investors showed much the same judgement. So the oxytocin did not make the investors generally more gullible or profligate: the effect was only visible when they had to deal with another human being.

"Oxytocin causes a substantial increase in trusting behaviour," Fehr and his colleagues reported, adding that they are performing a new round of experiments using brain imaging.

"Now that we know that oxytocin has behavioural effects, we want to know the brain circuits behind these effects," he said.

swissinfo with agencies

Key facts

Swiss scientists claim to have discovered neurobiological determinants of trust.
Test subjects who had a dose of the hormone oxytocin sprayed up their nose exhibited a marked increase in interpersonal trust.
Levels of oxytocin are also higher in people who are in love.

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