Anthony Lane

Oxytocin Makes People Trusting, Not Gullible

The neuropeptide oxytocin (OT) plays such a key role in social behavior that it has been referred to as “the love hormone” and “liquid trust” (e.g., Domes, Heinrichs, Michel, Berger, & Herpertz, 2007; Ferguson, Young, & Insel, 2002; Guastella, Mitchell, & Mathews, 2008; Morhenn, Park, Piper, & Zak, 2008; Taylor, 2006; Unkelbach, Guastella, & Forgas, 2008). These nicknames have an element of truth: When OT levels are increased, people do in fact seem to become more altruistic, trusting, and generous (Barraza & Zak, 2009; Baumgartner, Heinrichs, Vonlanthen, Fischbacher, & Fehr, 2008; Kosfeld, Heinrichs, Zak, Fischbacher, & Fehr, 2005; Pedersen, Ascher, Monroe, & Prange, 1982; Theodoridou, Rowe, Penton-Voak, & Rogers, 2009; Zak, Stanton, & Ahmadi, 2007). The effect of OT on prosocial behavior—and on trust in particular—is so strong that it has been suggested that OT may make people indiscriminately prosocial (e.g., trusting to a fault). While the press (e.g., Szalavitz, 2008) and researchers (e.g., Damasio, 2005) alike have worried about its potential misuse by politicians, the armed forces, and marketers, OT retailers have flourished by convincing clients that they can close deals with a few whiffs of OT. But does OT really increase people’s trust in anybody, or can contextual cues of unreliability override the effects of OT? Animal studies suggest that OT’s social effects may be context dependent (Campbell, 2008). In rodents, a female’s OT release after giving birth decreases her aggressiveness toward her offspring but increases her hostility toward potentially aggressive female intruders (Debiec, 2005; Pedersen, 2004). It is not known, however, whether OT’s effects are context dependent in humans. To examine this issue, we used a customized version of the trust game (Berg, Dickhaut, & McCabe, 1995; Cesarini et al., 2008; see the Supplemental Material available online). In this game, we manipulated partners’ trustworthiness and measured participants’ investment in each partner. We predicted higher investment by participants who received a nasal OT spray than by control participants, unless there were cues that a partner might not be trustworthy. Method

Is there a Publication Bias in Behavioural Intranasal Oxytocin Research on Humans? Opening the File Drawer of One Laboratory.

The neurohormone oxytocin (OT) has been one the most studied peptides in behavioural sciences over the past two decades. Primarily known for its crucial role in labour and lactation, a rapidly growing literature suggests that intranasal OT (IN‐OT) may also play a role in the emotional and social lives of humans. However, the lack of a convincing theoretical framework explaining the effects of IN‐OT that would also allow the prediction of which moderators exert their effects and when has raised healthy skepticism regarding the robustness of human behavioural IN‐OT research. Poor knowledge of the exact pharmacokinetic properties of OT, as well as crucial statistical and methodological issues and the absence of direct replication efforts, may have lead to a publication bias in the IN‐OT literature, with many unpublished studies with null results remaining buried in laboratory drawers. Is there a file drawer problem in IN‐OT research? If this is the case, it may also be true in our own laboratory. The present study aims to answer this question, document the extent of the problem and discuss its implications for OT research. For eight studies (including 13 dependent variables overall, as assessed through 25 different paradigms) performed in our laboratory between 2009 and 2014 on 453 subjects, the results obtained were too often not those that were expected. Only five publications emerged from our studies and only one of these reported a null finding. After realising that our publication portfolio has become less and less representative of our actual findings and because the nonpublication of our data might contribute to generating a publication bias in IN‐OT research, we decided to retrieve these studies from our drawer and encourage other laboratories to do the same.

Failed replication of oxytocin effects on trust: The envelope task case

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.

Psychoendocrinologie sociale de l'ocytocine : revue d'une littérature en pleine expansion

L’ocytocine (OT), une hormone polypeptidique bien connue pour son implication durant l’accouchement, suscite depuis plus de deux decennies un interet sans cesse grandissant dans la communaute scientifique. Ces recherches ont permis de mettre en avant le role crucial de l’OT dans les processus psycho-sociaux. A tel point qu’elle a ete elevee au rang d’hormone «pro sociale» par excellence. Mais cette reputation est-elle scientifiquement fondee ? L’OT est-elle vraiment l’hormone de l’amour decrite dans la presse populaire ? La revue de la litterature que nous avons menee vise a repondre a ces questions. Dans un premier temps, nous proposerons une revue exhaustive des differentes etudes menees sur l’OT. Nous fournirons dans un second temps un cadre interpretatif qui permettra de nuancer la vision que l’on se fait de l’OT a ce jour. Finalement, nous pointerons les failles presentes dans cette litterature et developperons certaines pistes de recherches pertinentes.