Scientists say hormone makes people more trusting
Jun. 1 2005
Trust in a bottle? It sounds like a marketer's fantasy, like the
fabled fountain of youth or the wild claims of fad diets.
Yet that's what Swiss and American scientists demonstrate in new
experiments with a nasal spray containing the hormone oxytocin. After
a few squirts, human subjects were significantly more trusting and
willing to invest money with no ironclad promise of a profit.
The researchers acknowledged their findings could be abused by con
artists or even sleazy politicians who might sway an election,
provided they could squirt enough voters on their way to the polls.
"Of course, this finding could be misused," said Ernst Fehr of the
University of Zurich, the senior researcher in the study, which
appears in Thursday's issue of the journal Nature. "I don't think we
currently have such abuses. However, in the future it could happen."
Other scientists say the new research raises important questions about
oxytocin's potential as a therapy for conditions like autism or social
phobias, in which trust is diminished. Or, perhaps the hormone's
activity could be reduced to treat more rare diseases, like Williams'
Syndrome, in which children have no inhibitions and approach strangers
"Might their high level of trust be due to excessive oxytocin
release?" asks University of Iowa neurologist Antonio Damasio, who
reviewed the experiments for Nature. "Little is known about the
neurobiology of trust, although the phenomenon is beginning to attract
Oxytocin is secreted in brain tissues and synthesized by the
hypothalamus. This small, but crucial feature located deep in the
brain controls biological reactions like hunger, thirst and body
temperature, as well as visceral fight-or-flight reactions associated
with powerful, basic emotions like fear and anger.
For years oxytocin was considered to be a straightforward reproductive
hormone found in both sexes. In both humans and animals, this chemical
messenger stimulates uterine contractions in labour and induces milk
production. In both women and men, oxytocin is released during sex,
Then, elevated concentrations of the hormone also were found in
cerebrospinal fluid during and after birth, and experiments showed it
was involved in the biochemistry of attachment. It's a sensible
conclusion, given that babies require years of care and the body needs
to motivate mothers for the demanding task of childrearing.
In recent years, scientists have wondered whether oxytocin also is
generally involved with other aspects of bonding behaviour - and
specifically whether it stimulates trust.
In the experiments, the 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 male students from universities in Zurich took part in
a pair of experiments. All the volunteers were in their 20s. They got
the oxytocin or a placebo.
In the first experiment, they played a game in which an "investor"
could choose to hand over to a "trustee" up to 12 units of money that
are each equal to .40 Swiss franc, or about 32 cents. The trustee
triples the investor's money, then gets to decide how much of the
proceeds to share. The trustee can't be certain how much - if anything
- he will get in return.
Of 29 subjects who got oxytocin, 45 per cent invested the maximum
amount of 12 monetary units and, in the researchers' words, showed
"maximal trust." Only 21 per cent had a lower trust level in which
they invested less than eight monetary units.
In contrast, the placebo group's trust behaviour was reversed. Only 21
per cent of the placebo subjects invested the maximum, while 45 per
cent invested at low levels.
Overall, the investors who received oxytocin invested 17 per cent more
than investors who received a placebo.
In a second experiment, investors faced the same decision. But this
time, the trustee was replaced by a computer program in an effort to
see whether the hormone promoted social interaction, or simply
With the computer, the oxytocin and placebo groups behaved similarly,
with both groups investing an average of 7.5 monetary units.
"Oxytocin causes a substantial increase in trusting behaviour," Fehr
and his colleagues reported.
Researchers said they are performing a new round of experiments using
brain imaging. "Now that we know that oxytocin has behavioural
effects," Fehr said, "we want to know the brain circuits behind these
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