Oxytocin → Interpersonal trust
A rise in Oxytocin does not identify a change in Interpersonal trust.
Intranasal oxytocin does not raise trusting behavior: a 2026 registered report found no effect in 211 people, and a pooled equivalence test with the 2020 registered replication (532 people) put the leftover effect inside a minimal range.
Randomized trial · High confidence · N=677
The association disappears when you account for other factors, like socioeconomic status or healthy-user bias.
Mechanism
Kosfeld, Heinrichs, Zak, Fischbacher, and Fehr (2005) reported that intranasal OT raised transfers in a real-stakes trust game. Nave, Camerer, and McCullough (2015) documented small samples, publication bias, and mixed follow-ups. Declerck, Boone, Pauwels, Vogt, and Fehr (2020) pre-registered a 677-person double-blind test with the original minimal-social-contact condition and found no OT effect on trusting behavior there. Exploratory post-hocs are not the registered claim. Krug, Fung, Liu, Treasure and colleagues (2024) randomized 149 female students to 24 IU OT or saline and ran a hypothetical investor game after the spray. Transfers did not differ. Kroll, Schruers, Viechtbauer, Vingerhoets, Seidel, Riedl, and Hernaus (2026) registered a large-scale replication of Kosfeld. Their own trial had 211 people. They found no evidence that the spray increased trusting behavior. Equivalence testing on that sample alone was inconclusive. They then merged their data with Declerck 2020, which they name as n=321, for a pool of 532. In the pool, equivalence testing put the OT effect inside a minimal range: too small, they write, for most lab studies. Baseline trust, reward sensitivity, and punishment sensitivity did not change the result. Another null does not raise the stamp.
Caveats
A contested trial stays on this page. The stamp is smoke for the folk spray-equals-trust arrow, not a claim that oxytocin is biologically inert. Krug's trust game used hypothetical money, no real pay, a deceived counterpart, and a between-subjects contrast run only after the spray. The sample was female university students. Emotion recognition is a different outcome. Kroll is available here only as an abstract. The n=211, the Declerck n=321 they pool, and the pooled n=532 are from that abstract. The sample size on this page stays Declerck's 677. Their own equivalence test was inconclusive. The minimal-range claim is the pooled test. Plasma oxytocin, parenting, and labor are different questions.
Effect
qualitative. Kosfeld 2005 reported higher transfers. Declerck 2020: no MSC main effect (N=677). Krug 2024: no group effect on a hypothetical trust game (N=149). Kroll 2026: no increase; pooled equivalence (n=532) puts the effect in a minimal range.
Nodes
Named confounders
Cite this page
What Causes What. “Oxytocin → Interpersonal trust.” https://whatcauseswhat.org/edges/e-oxytocin-trust (atlas updated 2026-09-02).
Papers
- Oxytocin increases trust in humans
M. Kosfeld, M. Heinrichs, P. J. Zak, U. Fischbacher, E. Fehr · 2005 · Nature
- Does Oxytocin Increase Trust in Humans? A Critical Review of Research
G. Nave, C. Camerer, M. McCullough · 2015 · Perspectives on Psychological Science
- A registered replication study on oxytocin and trust
C. H. Declerck, C. Boone, L. Pauwels, B. Vogt, E. Fehr · 2020 · Nature Human Behaviour
- The impact of oxytocin on emotion recognition and trust: Does disordered eating moderate these relationships?
I Krug, S Fung, S Liu, J Treasure, C Huang, K Felmingham, M Fuller-Tyszkiewicz, O McConchie · 2024 · PloS one
- Absence of a meaningful effect of intranasal oxytocin on trusting behavior: a registered report with pooled equivalence testing.
CF Kroll, KRJ Schruers, W Viechtbauer, C Vingerhoets, L Seidel, A Riedl, D Hernaus · 2026 · Cortex; a journal devoted to the study of the nervous system and behavior