[Pophealth] Trust and oxytocin administration
sabez at u.washington.edu
Thu Jun 2 09:54:38 PDT 2005
I've previously pointed out the relationship between oxytocin and trust,
and its relationship with income inequality (Uslaner's The Moral
Foundations of Trust and others). Today's premier journal, Nature,
carried the results of an experiment as well as an editorial (below) which
was rather typical for being written by an American and fearing politicans
would spray the stuff around during elections! The New York Times also
suggested the expected individual response. As DAvid Levitt pointed out,
NPR picked it up too. So we should mention the relationbship with income
inequality within the US and among countries (graphs on pg 41-2 of
WIlkinson's The Impact of Inequality).
Someday, perhaps in addition to nasal sprays for allergies and wheezing,
we'll carry a canister of oxytocin there with our iPod. But the basics
suggest that with our declining levels of trust in the US, our oxytocin
titers must be dropping. I don't think nasal sprays are the answer.
Trust, and Oxytocin administration
Damasio, A. (2005). ÒHuman behaviour Brain trust.Ó Nature 435(7042):
Kosfeld, M., M. Heinrichs, et al. (2005). ÒOxytocin increases trust in
humans.Ó Nature 435(7042): 673-676.
Nature June 2, 2005, 435 pg 571-2 HUMAN BEHAVIOUR Brain trust Antonio
As is the case with other social interactions, financial transactions
depend on trust. That fact is behind ingenious experiments that explore
the neurobiological underpinnings of human behaviour.
Michael Kosfeld and his colleagues got students in Zurich to play a
serious game. The game involved real monetary exchanges between two people
playing the anonymous roles of ÔinvestorÕ and ÔtrusteeÕ; beforehand, each
subject had received either the neuropeptide oxytocin or an inert placebo,
via nasal spray.
As a group, the investors who received oxytocin exhibited more trust in
the anonymous trustee than did the investors who received the placebo.
Because intranasally administered oxytocin crosses the blood-brain barrier
into the central nervous system, Kosfeld et al. (page 673 of this issue)1
conclude that the central action of oxytocin increases trusting behaviour;
and because the oxytocin spray did not change the behaviour of the
trustees, it seems that oxytocin only increases trust, not the reliability
of the trustee. This is a remarkable finding, and to explain its
significance we must first say a word about trust and about oxytocin
Given the polarities of reward and punishment that pervade biology at
various levels, trust is essential for the normal operation of human
societies. Remove trust and you compromise love, friendship, trade and
leadership. Little is known about the neurobiology of trust, although the
phenomenon is beginning to attract attention2.
As for oxytocin, it is a small peptide, consisting of nine amino acids,
that is produced mostly in the hypothalamus, the brainÕs master controller
of biological regulation, including emotion. Oxytocin acts both on certain
targets of the body (it is best known for inducing labour and lactation)
and on brain regions whose function is associated with emotional and
social behaviours (the amygdala and nucleus accumbens, for example) --
that is, it works both as a hormone and as a neuromodulator, a kind of
neurotransmitter. In animals, oxytocin contributes to social attachments,
including male and female bonding after mating, mother and infant bonding
after childbirth, and assorted sexual behaviours3,4. Besides triggering
complex and specific action-programmes, oxytocin may well work part of its
charm by selectively lowering the natural resistance that animals have to
the proximity of others, thus facilitating what is known as Ôapproach
Given this background, Kosfeld et al.1 hypothesized, reasonably and
perceptively, that oxytocin might be involved in trusting behaviour in
humans. After all, trust and approach behaviour are indelibly linked. We
commonly describe the child who approaches others with ease as ÔtrustingÕ,
and we use comparable descriptions for animals in similar situations.
Kosfeld and colleaguesÕ finding supports their hypothesis and opens the
way to a richer understanding of perhaps the most complex tier of human
social interactions. I once likened5 oxytocin to a love potion, the magic
elixir that makes Tristan fall for Isolde: add trust to the mix, for there
is no love without trust.
Kosfeld et al. provide an engaging discussion of the possible mechanisms
behind their finding. They reject the possibility that oxytocin has a
nonspecific positive effect on social behaviour, because of its different
influence on investors and trustees. Approach and trust possibly dominate
the behaviour of investors, and that is where oxytocin works, whereas
trustee behaviour is dominated by a principle of reciprocity, for which
oxytocin seems irrelevant. Kosfeld et al. also reject the possibility that
oxytocin merely reduces the sensitivity to risk, because in a control
experiment in which the investors knew the trustee was a computer, they
did not take any extra risks. The authors finally settle for an attractive
pair of factors: that oxytocin overcomes the aversion to betrayal (which
applies only to the investors), and that this is combined with the effects
of reward that result from enhanced approach behaviour.
The significance of the study lies in what it can tell us about
non-experimental circumstances, when the equivalent of an investor is not
sniffing oxytocin. What might be happening then? First, perceiving certain
social configurations probably leads to oxytocin release in selected brain
regions -- that is, the cognitive appraisal of a situation, based on an
individualÕs genetic make-up and past experience, triggers a chain of
neural events that includes (but is not limited to) the release of
oxytocin. Second, oxytocin modulates the activity of cognitive neural
networks, resulting in enhanced trusting behaviour. Whether this result is
achieved via a mostly unconscious bias (by altering the competition among
ensembles of neurons that represent varied choice options), or a conscious
deliberative process, remains to be established -- although the evidence
seems to favour the former possibility in the current experiment. However,
the input, along the cognitive chain, of neural events arising in brain
areas associated with social and emotional responses is a requisite part
of the explanation. The finding points to the crucial involvement of
emotional phenomena in the processes leading from cognition to behaviour.
The authorsÕ results open up possibilities for investigating conditions in
which trust is either diminished, as in autism, or augmented. For example,
patients with bilateral damage to the amygdala approach strangers with
unusual ease, and fail to recognize untrustworthy individuals whom normal
people would resolutely avoid6. In this case, damage to the amygdala may
prevent the detection of the potential threat evoked by certain stimuli.
And children with Williams syndrome, a rare genetic disorder, approach
strangers fearlessly and indiscriminately7. Might their high level of
trust be due to excessive oxytocin release?
Some may worry about the prospect that political operators will generously
spray the crowd with oxytocin at rallies of their candidates. The scenario
may be rather too close to reality for comfort, 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. Civic
alarm at the prospect of such abuses should have started long before this
study, and the authors cannot be blamed for raising it. Whatever the
beneficial biomedical applications, or the abuses, may turn out to be,
Kosfeld et al. have made a valuable contribution to our understanding of
the role of neuromodulators in human behaviour that involves choice.
¥ Antonio Damasio is in the Department of Neurology, University of Iowa
College of Medicine, 200 Hawkins Drive, Iowa City, Iowa 52242, USA.
e-mail: antonio-damasio at uiowa.edu
1. Kosfeld, M., Heinrichs, M., Zak, P. J., Fischbacher, U. & Fehr, E.
Nature 435, 673-676 (2005).
2. King-Casas, B. et al. Science 308, 78-83 (2005).
3. Carter, C. S. Psychoneuroendocrinology 23, 779-818 (1998).
4. Insel, T. R. & Shapiro, L. E. Proc. Natl Acad. Sci. USA 89, 5981-5985
5. Damasio, A. R. DescartesÕ Error: Emotion, Reason, and the Human Brain
(Penguin, New York, 1994).
6. Adolphs, R. & Damasio, A. R. Nature 393, 470-474 (1998).
7. Doyle, T. F. et al. Am. J. Med. Genet. 124A, 263-273 (2004).
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