Universiteit Leiden

nl en

Research project

Role of pupil-synchronisation in trust

Here I propose to study the relationship between autonomic pupil-synchronisation and trust, at the behavioural and neural level, and examine a targeted set of possible contextual moderators.

2014 - 2018
Mariska Kret
NWO Veni grant NWO Veni grant

Many daily decisions are made through quick evaluations of another's trustworthiness, especially when the decision involves strangers. In this process, individuals rely on a partner's tractable characteristics, such as group membership, facial expression and eye gaze. Intriguingly, my own recent research suggests that individuals also respond to their partner's pupil-size (Kret, Tomonaga & Matsuzawa, in press). Pupil-size is an interesting social signal, because it cannot be controlled or faked, in contrast to features such as eye gaze and expression. I showed that seeing someone's pupils dilate promotes trust. In addition, I showed that people synchronize their pupil-size with an observed person. 

These unprecedented findings suggest a link between autonomic pupil-synchronization and trust. Here I propose to study this relationship at the behavioural and neural level, and examine a targeted set of possible contextual moderators.

  1. Objective 1 is to test whether pupil-synchronization with dilating pupils provides feedback that the interaction partner is trustworthy.
  2. Objective 2 is to test the neuro-hormonal mechanisms. I predict that pupil-synchronization and subsequent development of trust shows neural overlap with empathy and is strengthened by oxytocin, a hypothalamic neuropeptide involved in social bond-formation and pro-social behavior.
  3. Objective 3 is to examine possible moderators by manipulating in/out-group characteristics of the observed.

Objective 1 and 3 involve behavioural experiments that manipulate observed or, innovatively, participant's pupil-size and measures, through eye-tracking technology, the putative link between pupil-synchronization and trust. Objective 2 involves an extensive fMRI/eye-tracking study in which oxytocin (vs. placebo) is manipulated, enabling to uncover the neuro-hormonal mechanisms that engage when people synchronize with another's pupil-size. The project primarily intends to build and test new theory, but also has applied relevance for patient care.


  • Kret, M.E., & de Dreu, C.K.W. (in press). Pupil-mimicry conditions trust in exchange partners: Moderation by oxytocin and group membership. The Royal Society B-Biological Sciences.
  • Kret, M.E., Fischer, A.H. & de Dreu, C.K.W. (2015). Pupil-mimicry correlates with trust in in-group partners with dilating pupils. Psychological Science, 26(9), 1401-1410. I = 4.43. Download.
  • Kret, M.E. (2015). Emotional expressions beyond facial muscle actions. A call for studying autonomic signals and their impact on social perception. Frontiers in Psychology, 6, 711.  I = 2.800. Download.
This website uses cookies.  More information.