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Study · Randomized controlled trial · 2017

4 results

Pupil-mimicry conditions trust in partners: moderation by oxytocin and group membership.

Kret ME, De Dreu CK

Proceedings. Biological sciences1 Mar 2017Cited by 42 (Europe PMC)

PMID28250181 (opens in a new tab)PMCIDPMC5360920 (opens in a new tab)DOI10.1098/rspb.2016.2554 (opens in a new tab)PepBankPUB-28250181
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Summary

Across species, oxytocin, an evolutionarily ancient neuropeptide, facilitates social communication by attuning individuals to conspecifics' social signals, fostering trust and bonding. The eyes have an important signalling function; and humans use their salient and communicative eyes to intentionally and unintentionally send social signals to others, by contracting the muscles around their eyes and pupils. In our earlier research, we observed that interaction partners with dilating pupils are trusted more than partners with constricting pupils. But over and beyond this effect, we found that the pupil sizes of partners synchronize and that when pupils synchronously dilate, trust is further boosted. Critically, this linkage between mimicry and trust was bound to interactions between ingroup members. The current study investigates whether these findings are modulated by oxytocin and sex of participant and partner. Using incentivized trust games with partners from ingroup and outgroup whose pupils dilated, remained static or constricted, this study replicates our earlier findings. It further reveals that (i) male participants withhold trust from partners with constricting pupils and extend trust to partners with dilating pupils, especially when given oxytocin rather than placebo; (ii) female participants trust partners with dilating pupils most, but this effect is blunted under oxytocin; (iii) under oxytocin rather than placebo, pupil dilation mimicry is weaker and pupil constriction mimicry stronger; and (iv) the link between pupil constriction mimicry and distrust observed under placebo disappears under oxytocin. We suggest that pupil-contingent trust is parochial and evolved in social species in and because of group life.
CC BYText from Europe PMC. Highlighted sentences are the source of results.

Results from this study4

4 results from studies that gave the peptide. 4 results from people.

  1. 01HumanRandomized controlled trialMechanism

    In male participants in incentivized trust games, trust in partners with dilating pupils was extended and trust in partners with constricting pupils was withheld, especially with oxytocin rather than placebo.

    In plain wordsIn men, oxytocin strengthened trust in partners whose pupils widened and distrust of partners whose pupils narrowed, compared with placebo.

    Peptide
    Oxytocin
    Outcome
    IncreaseTrust in partners by pupil dilation (men)
    Study

    n: not reported in source

    Comparator
    Placebo
    Outcome group
    Social behavior and cognition · Mental health and mood
    Studied dose
    Dose not stated

    Source sentences

    Summary
    male participants withhold trust from partners with constricting pupils and extend trust to partners with dilating pupils, especially when given oxytocin rather than placebo
    1 context sentence
    Summary · context
    Using incentivized trust games with partners from ingroup and outgroup whose pupils dilated, remained static or constricted, this study replicates our earlier findings.
  2. 02HumanRandomized controlled trialMechanism

    In female participants in incentivized trust games, the trust in partners with dilating pupils was blunted under oxytocin compared with placebo.

    In plain wordsIn women, oxytocin lowered the extra trust placed in partners whose pupils widened, compared with placebo.

    Peptide
    Oxytocin
    Outcome
    DecreaseTrust in partners with dilating pupils (women)
    Study

    n: not reported in source

    Comparator
    Placebo
    Outcome group
    Social behavior and cognition · Mental health and mood
    Studied dose
    Dose not stated

    Source sentences

    Summary
    female participants trust partners with dilating pupils most, but this effect is blunted under oxytocin
    1 context sentence
    Summary · context
    Using incentivized trust games with partners from ingroup and outgroup whose pupils dilated, remained static or constricted, this study replicates our earlier findings.
  3. 03HumanRandomized controlled trialMechanism

    In incentivized trust games, oxytocin rather than placebo made pupil dilation mimicry weaker and pupil constriction mimicry stronger.

    In plain wordsUnder oxytocin, people copied widening pupils less and narrowing pupils more than under placebo.

    Peptide
    Oxytocin
    Outcome
    MixedPupil dilation and constriction mimicry
    Study

    n: not reported in source

    Comparator
    Placebo
    Outcome group
    Social behavior and cognition · Mental health and mood
    Studied dose
    Dose not stated

    Source sentences

    Summary
    under oxytocin rather than placebo, pupil dilation mimicry is weaker and pupil constriction mimicry stronger
    1 context sentence
    Summary · context
    Using incentivized trust games with partners from ingroup and outgroup whose pupils dilated, remained static or constricted, this study replicates our earlier findings.
  4. 04HumanRandomized controlled trialMechanism

    In incentivized trust games, the link between pupil constriction mimicry and distrust seen under placebo disappeared under oxytocin.

    In plain wordsThe link between copying narrowing pupils and distrust, seen with placebo, was gone under oxytocin.

    Peptide
    Oxytocin
    Outcome
    DecreaseLink between constriction mimicry and distrust
    Study

    n: not reported in source

    Comparator
    Placebo
    Outcome group
    Social behavior and cognition · Mental health and mood
    Studied dose
    Dose not stated

    Source sentences

    Summary
    the link between pupil constriction mimicry and distrust observed under placebo disappears under oxytocin
    1 context sentence
    Summary · context
    Using incentivized trust games with partners from ingroup and outgroup whose pupils dilated, remained static or constricted, this study replicates our earlier findings.

AI wrote and checked these results. AI can make mistakes, so check important results against the source.

Version history

PepBank keeps every version of the data on this study. Status changes from Retraction Watch, Europe PMC and Crossref are listed with their source.

  1. Version 2Current

    11 Oct 2026, 01:30 UTC

    Study results updated

  2. Version 1

    9 Oct 2026, 02:49 UTC

    First added · source update from Europe PMC

Subjects

Terms as the source lists them.

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