How the brain reacts to breach of trust

Scientists at the University of Zurich have discovered the neurophysiological basis of human trust and the reaction to it being breached. They have been able to prove that oxytocin promotes a sentiment of trust, even after a betrayal. The research team led by neuroscientist Ernst Fehr has therefore succeeded in taking a further step towards understanding trust. The study will be appearing on 22nd May 2008 in the scientific magazine «Neuron» (volume 58, issue 4). 

The ability of human beings to live in societies is based on trust. Whether in love or politics, in family or business life, trust always plays an important role. The interest was correspondingly high when researchers at the University of Zurich discovered three years ago that oxytocin promotes a feeling of trust. However, the neurophysiological basis of that effect and why oxytocin increases trust remained unknown. Another unanswered question was whether oxytocin can influence the behaviour of trust, even after one person's faith in another has been betrayed. 

A research team at the University of Zurich with the neuroscientist Thomas Baumgartner, the neuroeconomist Ernst Fehr and the psychologist Markus Heinrichs has now determined that oxytocin exerts an influence on how human beings deal with a breach of trust. Test subjects who received a placebo reacted to a betrayal of trust by a reduction in their level of trust. On the other hand, people who received oxytocin by means of a nasal spray did not change their trusting behaviour. 

This differing reaction to a breach of trust is associated with a very specific activation pattern in the brain. Test subjects who received oxytocin demonstrated a lower activation in the amygdala, in regions of the midbrain and in the dorsal nucleus of the caudatus. This pattern indicates that oxytocin reduces the activation in those structures of the brain which are involved not only in dealing with fear but also in the adaptation of behaviour following a negative experience such as a betrayal of trust. 

These new findings could help in gaining more profound knowledge of mental disorders in which a social deficit is at the forefront. As explained by the psychologist Markus Heinrichs, clinical studies are being examined in which an intranasal administration of oxytocin is combined with standardised behavioural therapy in the treatment of disorders such as social phobia and borderline personality dysfunction. The neuroscientist Thomas Baumgartner hopes that the results will lead to fertile research into mental disorders of that kind. «Particularly the knowledge about where in the brain the effect of oxytocin manifests itself could help in the development of even better therapeutic measures.» 

The neuroeconomist Ernst Fehr adds: «We have discovered significant elements of the neural basis of trust after a betrayal of trust has taken place. In view of the importance of trust in human social interaction, these results open up the possibility of being able to fathom and increase our general understanding of the neurophysiological basis of prosocial behaviour.»