There is no difference in contagious yawning between men and women

Abstract

Norscia et al. [1] recently reported the first evidence for a sex bias in contagious yawning among humans. Based on previous research showing an indirect connection between contagious yawning and empathy (e.g. [2-4], but see [5,6]) and that levels of empathy appear to be higher in women compared with men (e.g. [7][8][9]), the authors investigated whether there is also a sex difference in the expression of contagious yawning through an observational study on humans. By examining 92 dyads already showing evidence of contagious yawning, which was a subset of a much larger sample of individuals, Norscia et al. report that both social bond and sex were significant predictors of this response. In particular, contagious yawning was more common if the dyad was strongly bonded and when the individual catching the yawn was female.Here, we call into question these conclusions about a sex difference in contagious yawning. First, we draw attention to more than a dozen previous publications on contagious yawning in humans, many of which were not cited by Norscia et al.showing no difference in susceptibility to yawn contagiously and/or contagious yawning frequency between men and women. Similarly, we do the same for nearly a dozen unacknowledged publications in the comparative literature. Lastly, we challenge the validity of the reported sex difference within the Norscia et al. study itself, based on their analysis of only a restricted subset of documented contagious yawners.A close examination of the empirical literature clearly shows that the sex difference reported by Norscia et al. stands in stark contrast to previous findings on contagious yawning in humans. While Norscia et al. only reference a single publication that did not find a difference in the frequency of contagious yawning between men and women [5], we provide references to an additional 14 papers showing no effect (two of which were in fact written by some of the Norscia et al. authors in question; table 1).

Contagious yawning, empathy, and their relation to prosocial behavior.

“…However, this difference is statistically not significant (χ 2 = .97, p = .32, df = 1, N = 354) confirming the result of various other studies (e.g. Gallup and Massen 2016). However, the IRI shows clearly higher values for women.…”

Difference in contagious yawning between susceptible men and women: why not?

“…We therefore selected the articles that were relevant to our comparative and evolutionary approach. Gallup & Massen [ 1 ] state that the gender difference in yawn contagion detected in our study is a false positive and that the null effect is real. Unfortunately, the sample that they used to make this assumption (17 negative cases and one positive case) is incorrect and, consequently, so is their conclusion.…”

“…In their commentary, Gallup & Massen [ 1 ] criticize the fact that we did not consider ‘more than a dozen’ previous publications which did not report gender differences in human contagious yawning. We thank the authors for pointing out this issue and for giving us the possibility to provide a brief explanation on some aspects that are not as obvious as we thought.…”

“…The possibility to find a phenomenon relies on whether the sample and the methodology used are suitable to detect it. To retain the metaphor used by Gallup & Massen [ 1 ], you can flip a coin as many times as you want and never find what you expect if what you expect is to get a six. You should change the approach and roll a dice, instead.…”

“…The results presented in the article by Palagi et al [ 2 ] were based on naturalistic observations (and not on videos as it is said in table 1 of the commentary [ 1 ]) and the database also included bonobos, in which the sex of the trigger and not the sex of the responder tended to influence yawn contagion rates [ 3 ]. Therefore, it could not be used to evaluate which variables affect yawn contagion rates in humans only.…”