title: Failed Replication of Oxytocin Effects on Trust: The Envelope Task Case.
abstract: The neurohormone Oxytocin (OT) has been one of the most studied peptides in behavioral sciences over the past two decades. Many studies have suggested that OT could increase trusting behaviors. A previous study, based on the "Envelope Task" paradigm, where trust is assessed by the degree of openness of an envelope containing participant's confidential information, showed that OT increases trusting behavior and reported one of the most powerful effects of OT on a behavioral variable. In this paper we present two failed replications of this effect, despite sufficient power to replicate the original large effect. The non-significant results of these two failed replications clearly exclude a large effect of OT on trust in this paradigm but are compatible with either a null effect of OT on trust, or a small effect, undetectable with small sample size (N = 95 and 61 in Study 1 and 2, respectively). Taken together, our results question the purported size of OT's effect on trust and emphasize the need for replications.
authors.affiliation: Université catholique de Louvain, Department of Psychology, Louvain-La-Neuve, Belgium.
authors.forename: Anthony
authors.initials: A
authors.lastname: Lane
authors.affiliation: Université catholique de Louvain, Department of Psychology, Louvain-La-Neuve, Belgium.
authors.forename: Moïra
authors.initials: M
authors.lastname: Mikolajczak
authors.affiliation: University of Denver, Department of Psychology, Denver, Colarado, United State of America.
authors.forename: Evelyne
authors.initials: E
authors.lastname: Treinen
authors.affiliation: Université catholique de Louvain, Department of Psychology, Louvain-La-Neuve, Belgium.
authors.forename: Dana
authors.initials: D
authors.lastname: Samson
authors.affiliation: Université catholique de Louvain, Department of Psychology, Louvain-La-Neuve, Belgium.
authors.forename: Olivier
authors.initials: O
authors.lastname: Corneille
authors.affiliation: Université catholique de Louvain, Department of Neurology and Psychiatry, Woluwe-Saint-Lambert, Belgium.
authors.forename: Philippe
authors.initials: P
authors.lastname: de Timary
authors.affiliation: Université catholique de Louvain, Department of Psychology, Louvain-La-Neuve, Belgium.
authors.forename: Olivier
authors.initials: O
authors.lastname: Luminet
mesh_terms: D000328:Adult; D001519:Behavior / Q000187:drug effects*; D006801:Humans; D008297:Male; D010121:Oxytocin / Q000008:administration & dosage* / Q000009:adverse effects; D035502:Trust
chemical_list: D010121:Oxytocin