Null results of oxytocin and vasopressin administration across a range of social cognitive and behavioral paradigms: Evidence from a randomized controlled trial

Abstract

Research examining oxytocin and vasopressin in humans has the potential to elucidate neurobiological mechanisms underlying human sociality that have been previously unknown or not well characterized. A primary goal of this work is to increase our knowledge about neurodevelopmental and psychiatric disorders characterized by impairments in social cognition. However, years of research highlighting wide-ranging effects of, in particular, intranasal oxytocin administration have been tempered as the fields of psychology, neuroscience, and other disciplines have been addressing concerns over the reproducibility and validity of research findings. We present a series of behavioral tasks that were conducted using a randomized, double-blind, placebo controlled, between-subjects design, in which our research group found no main effects of oxytocin and vasopressin on a host of social outcomes. In addition to null hypothesis significance testing, we implemented equivalence testing and Bayesian hypothesis testing to examine the sensitivity of our findings. These analyses indicated that 47-83% of our results (depending on the method of post-hoc analysis) had enough sensitivity to detect the absence of a main effect. Our results add to evidence that intranasal oxytocin may have a more limited direct effect on human social processes than initially assumed and suggest that the direct effects of intranasal vasopressin may be similarly limited. Randomized controlled trial registration: NCT01680718.

Keywords: Oxytocin; Social behavior; Social cognition; Social processes; Vasopressin.

Figure 1.

Visualized equivalence tests are shown for each of the 18 comparisons, respectively for OT and AVP versus PLA, across the six tasks. For each comparison, the Cohen’s d (diamonds), confidence intervals for mean difference (MD interval; thick lines), effect size confidence intervals (ES interval; thin lines), and raw score equivalence bounds (grey rectangles) are shown. Both confidence intervals were Bonferroni corrected (see Table 1 for corrected alpha levels). If an ES interval does not include zero, the NHST test is statistically significant. If an MD interval lies within the equivalence bounds and ES interval includes zero then the test supports the null hypothesis. If an ES interval includes zero and a MD interval crosses one of its equivalence bounds, then the test is insensitive for any decision. Adapted from Quintana (2018).

Figure 2.

Graph showing how the width (r value, shown on the X axis) of different prior distributions influences Bayes Factor scores (BF, shown on Y axis) from the Bayesian t-test results. Here the “user prior” is JASP’s default Cauchy distribution (r=.707) yields relative evidence in favor of the null hypothesis that is below BF=3, while the more standard Jeffreys’ prior (r=1) is greater than three, indicating evidence analogous to a moderate effect. Data shown is from the interpersonal distance task in which we tested the effects of receiving AVP versus PLA nasal sprays on the change in female participants’ trustworthiness judgments between faces that appeared nearby and far away.