From Berkay İlber Tunakan’s master’s thesis, supervised by Prof. Dr. Aydın Akan. The study is ongoing; see our research page for details.
You download a new banking app. A company you have never heard of promises you a high interest rate. On the other side is the bank you have used for years, one you may not even like, but that is “at least familiar”. Which one do you trust with your money?
Most of us answer within seconds. But in those few seconds, the brain runs an incredibly complex calculation: Will this brand keep its promise? What if I lose? Has it let me down before? What is my gut telling me?
The Classic Way To Measure Trust: The Investment Game
Economists and neuroscientists have long used a simple but powerful game to measure trust. In the investment game, one player is given money and asked to send part of it to another player. The money sent is multiplied, and the other player decides how much to send back. How much you send is a measure of how much you trust the other person [1].
Studies with this game have produced striking results. In one study, participants given oxytocin, the so-called “bonding hormone”, via nasal spray sent noticeably more money to the other player [2]. It was a vivid sign that trust is not just a rational decision: the body and the brain’s chemistry are involved too.
Trust Is Not In One Place In The Brain
Brain imaging studies show that there is no single “trust centre”. Regions that compute expected reward, structures that evaluate risk and threat, and frontal regions that weigh the decision all work together [3]. EEG studies likewise find trust-related activity spread across different regions of the head [4].
When brands enter the picture, things get even more complex. Recognising a brand, liking it and trusting it are not the same. Trust in a familiar brand and trust in a brand we have just met may be processed by different routes in the brain. A known reputation is even known to change how much attention a person pays to new information [3].
Not Imposing Labels On The Brain
Most EEG studies of trust start with a label: each moment is marked “trusted” or “did not trust”, and an AI model tries to predict that label from the brain signal. The problem with this approach is that it squeezes expectation, risk, remembered experience and felt closeness into a single word.
We turn the question around. Instead of telling the brain “this is trust”, we ask it: How do EEG patterns recorded at moments of trust decisions group together by their similarity to one another? For this we use a kind of AI called unsupervised learning. These methods find the natural groups in the data on their own, without being told the right answer. It is like sorting a box of mixed buttons by colour, size and number of holes without anyone telling you how.
Once these groups emerge, the really interesting part begins: Do the clusters the brain forms on its own match the brand’s familiarity, whether it is liked, the participant’s decision, or the outcome of that decision?
How We Work
Our participants play an investment game featuring well-known brands from different sectors. In each round they decide whether to invest in a brand and see the outcome. Some brands live up to the trust placed in them, while others disappoint over time. This lets us observe trust being built, maintained and broken within the same experiment.
Throughout the game we record EEG and match every decision moment to the brain signal with millisecond precision using an experiment interface we developed ourselves. Participants also fill in a questionnaire measuring how much they trust the brands.
Why It Matters
Trust is the invisible currency of the economy. It underlies many of our decisions, from which bank we use and which medicine we take to which app we trust with our data. Understanding how trust is built and broken in the brain can help brands build a more honest relationship with consumers, and help us understand our own decisions better.
We will write about the results here when we are ready to share them.
References
- Berg, J., Dickhaut, J., McCabe, K. (1995). Trust, reciprocity, and social history. Games and Economic Behavior, 10(1), 122–142. doi:10.1006/game.1995.1027
- Kosfeld, M., Heinrichs, M., Zak, P. J., Fischbacher, U., Fehr, E. (2005). Oxytocin increases trust in humans. Nature, 435, 673–676. doi:10.1038/nature03701
- Riedl, R., Javor, A. (2012). The biology of trust: Integrating evidence from genetics, endocrinology, and functional brain imaging. Journal of Neuroscience, Psychology, and Economics, 5(2), 63–91. doi:10.1037/a0026318
- Wang, M. et al. (2018). EEG-based neural correlates of trust in human-autonomy interaction. IEEE Symposium Series on Computational Intelligence (SSCI), 350–357. doi:10.1109/SSCI.2018.8628649