"Animal spirits" and hormones: understanding trust in interpersonal interactions

Prosperity in all aspects of social life, from interpersonal relationships to economic or political relationships, depends on human cooperation and trust. The concept of trust is particularly relevant these days, as some economists have attributed the ebbs and flows of the economy to irrational fluctuations in our confidence in others. Trust will be defined as the subjective expectation that others will not harm or disadvantage us in instances when they have an opportunity to do so. Accordingly, trust decisions will be defined as the decisions that give others such an opportunity. Why do people differ in the ways and degrees in which they trust familiar or unfamiliar others in given interpersonal situations? What dynamic interplay of parameters determines trust decisions in interpersonal interactions? Can such decisions be facilitated or inhibited by some intervention and how? These questions are at the heart of this project. To answer these questions we will design experiments that entail 'on-line' interpersonal exchanges and will model the complexity of human behaviour in these interactions using advanced methods. We will measure the dynamic influence of various individual traits and social signals (e.g. 'trustworthy' behaviour by others) on people's decisions to trust others. In this endeavour, we will use the oxytocin system as a tool.

The oxytocin system in the brain may be one of the main mechanisms driving individual differences in the expression of interpersonal trust. In animal studies, scientists have discovered that this neural system, which uses the hormone oxytocin to communicate with other brain areas, plays a key role in inter-species differences in social behaviour, as well as in differences between members of the same species. For example, the oxytocin system has been shown to influence the formation of lasting attachments with one's offspring or peers, the display of caring behaviour towards offspring or partners, social play, the recognition of one's partner's or offspring's by their odour, or the display of distress by offspring when abandoned. While there is also accumulating evidence that the function of the oxytocin system also influences social behaviour in humans, almost nothing is known regarding how the oxytocin system is organised in the human brain. We also know next to nothing about the possible existence of gender differences (as is the case with other species), about how this system is linked with differences in human social preferences, including decisions to trust, and about how this system can exert a dynamic influence on the processes underlying judgements of trustworthiness and decisions to trust.

In this project, we will use state-of-the-art neuroimaging techniques and innovative data modelling and analysis methods to try and shed some light on these questions. We hope to generate new findings that will make a significant contribution to understanding the processes driving trust behaviour, as well as to generate new evidence about the oxytocin system in the human brain, which will be of direct interest across a range of disciplines.

The successful completion of this project will generate urgently needed findings that will be directly relevant and translatable not only to several research domains, but also to any domains of social life based on interpersonal relationships and trust.

Some of the potential benefits of this project for non-academic beneficiaries are:

(1) Intranasal oxytocin has started to emerge as a potential adjunct treatment for disorders with deficits in the processing of social information (e.g. autism), social skills (e.g. borderline personality disorder) or with anxiety and depression symptoms. While the proposed work does not directly assess the efficacy of oxytocin as a treatment for these conditions, we hope it will provide some important new findings that may guide psychiatric applications and benefit patient groups. Specifically:

- The information on the pharmacokinetics and pharmacodynamics of oxytocin in the human brain will provide the necessary basic science information for the optimal design of clinical trials using intranasal oxytocin.
- We will try to link, for the first time, differences in the geography of oxytocin receptors with differences in social behaviour. Animal research suggests that this, and not the increase in the volume of released oxytocin in the brain, is the critical factor underpinning social behaviour. This is an important issue to take into consideration when examining the use of intranasal sprays as an adjunct therapy, e.g. in autism.
- We will generate information regarding gender differences in (a) the oxytocin system in the human brain, (b) the effects of intranasal oxytocin on human behaviour and (c) the link between brain and behaviour. These findings could inform decisions regarding the potential use of oxytocin in the case of disorders with marked gender differences. Examples include the treatment of social deficits in autistic spectrum disorders, or in the treatment of anxiety and depression symptoms in mood disorders.

(2) Drug companies and neuropsychopharmacologists developing new compounds to act on the central nervous system may benefit from our research, as it will contribute to the development of a new non-invasive methodological approach to investigate the effects of compounds in the central nervous system, and estimate information about their pharmacokinetics and pharmacodynamics.

(3) We expect that the findings we will generate will be of great interest to the general public. Findings from the nascent field of oxytocin research often make the news headlines, indicating that they have a wider societal appeal. This is because oxytocin is believed to be involved in all quintessential aspects of human social life - love, sex, trust, morality to name a few. The effects of oxytocin sprays may be exaggerated by the news media when they talk about the "hormone of love", the "moral molecule" or the "trust hormone", or when concerns are raised about potential abuse, e.g. by political propaganda. But trust is the implicit fabric of our societies, the basis of our interpersonal as well as social and political relations, of which we understand so little in experimental psychology and neuroscience. We expect that the wider audience will be interested in our findings, and we will undertake an ambitious public dissemination program to this effect (see Pathways to impact).

Therefore, the outcomes of this project are expected to have both health care and societal impact.