Oxytocin Is BS!!!
The claim that the hormone oxytocin promotes trust in humans has drawn a lot of attention. But today, a group of researchers reported that they’ve been unable to reproduce their own findings concerning that effect.
The new paper, in
PLoS ONE, is by Anthony Lane and colleagues from Louvain in Belgium. The same team have previously published evidence supporting the link between oxytocin and trust.
Back in 2010 they reported that “oxytocin increases trust when confidential information is in the balance”. An intranasal spray of oxytocin made volunteers more likely to leave a sensitive personal document lying around in an open envelope, rather than sealing it up, suggesting that they trusted people not to peek at it.
https://www.sciencedirect.com/science/article/pii/S0301051110001729
However, the authors now say that they failed to replicate the 2010 ‘envelope task’ result in two subsequent studies.
Lane et al. conclude that “The non-significant results of these two failed replications clearly exclude a large effect of oxytocin on trust in this paradigm… Taken together, our results question the purported size of oxytocin’s effect on trust and emphasize the need for replications.”
But then, why did the original study find such a large effect?
Lane et al. point out that it’s extremely unlikely that the original effect was just a fluke: the effect size in the 2010 study was enormous, and the effect was highly significant at p<0.001.
Instead, the authors suggest that the effect may have been driven by ‘unconscious behavioral priming’. The 2010 study was only single-blind – the participant didn’t know whether they were getting oxytocin or placebo but the experimenter did know. The researchers might have behaved differently towards the participants based on that knowledge. Plausibly, this could have made the participants feel more or less comfortable. The replications were double-blind and so were immune to this bias. So maybe that was the problem all along.
Lane A, Mikolajczak Mr, Treinen E, Samson D, Corneille O, et al. Failed Replication of Oxytocin Effects on Trust: The Envelope Task Case. PLoS ONE. 2015;10(9):e0137000. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137000
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.
