Abstract
ABSTRACTEarlier work found that – compared to participants who adopted constrictive body postures – participants who adopted expansive body postures reported feeling more powerful, showed an increase in testosterone and a decrease in cortisol, and displayed an increased tolerance for risk. However, these power pose effects have recently come under considerable scrutiny. Here, we present a Bayesian meta-analysis of six preregistered studies from this special issue, focusing on the effect of power posing on felt power. Our analysis improves on standard classical meta-analyses in several ways. First and foremost, we considered only preregistered studies, eliminating concerns about publication bias. Second, the Bayesian approach enables us to quantify evidence for both the alternative and the null hypothesis. Third, we use Bayesian model-averaging to account for the uncertainty with respect to the choice for a fixed-effect model or a random-effect model. Fourth, based on a literature review, we obtained an empirically informed prior distribution for the between-study heterogeneity of effect sizes. This empirically informed prior can serve as a default choice not only for the investigation of the power pose effect but for effects in the field of psychology more generally. For effect size, we considered a default and an informed prior. Our meta-analysis yields very strong evidence for an effect of power posing on felt power. However, when the analysis is restricted to participants unfamiliar with the effect, the meta-analysis yields evidence that is only moderate.
Highlights
Could adopting a powerful body posture make us more powerful? Carney, Cuddy, and Yap (2010) found that participants who adopted expansive, high-power body postures (Figure 1, top row) as opposed to constrictive, low-power body postures (Figure 1, bottom row) reported feeling more powerful and in charge, showed an increase in testosterone and a decrease in cortisol, and displayed an increased tolerance for risk
The first step in our analysis was to compute one-sided Bayesian t-tests (Rouder, Speckman, Sun, Morey, & Iverson, 2009; Ly, Verhagen, & Wagenmakers, 2016; Gronau, Ly, & Wagenmakers, 2017). This allowed us (1) to estimate for each study the posterior distribution of the standardized effect size that represents our beliefs about the effect size after having observed the data of that study and (2) to quantify the evidence that each study provides in favor of the hypothesis that the power pose effect is positive (H+) versus the null hypothesis that the effect is zero (H0)
We present the results obtained under two alternative prior choices for between-study heterogeneity: (1) the maximum-likelihood inversegamma distribution; and (2) a Beta(1, 2) prior distribution
Summary
Could adopting a powerful body posture make us more powerful? Carney, Cuddy, and Yap (2010) found that participants who adopted expansive, high-power body postures (Figure 1, top row) as opposed to constrictive, low-power body postures (Figure 1, bottom row) reported feeling more powerful and in charge, showed an increase in testosterone and a decrease in cortisol, and displayed an increased tolerance for risk. Instead of adopting one model for inference and ignoring the other model entirely, we can weight the results of both models according to their posterior plausibilities This yields a model-averaged measure of evidence and a modelaveraged estimate for the meta-analytic effect size. Based on an extensive literature review of meta-analyses in the field of psychology, we obtained an informed prior distribution for the between-study heterogeneity. This informed prior distribution can serve as an informed default for the investigation of the power pose effect in the present meta-analysis, but for the field of psychology more generally. As a robustness check with respect to the prior choice we show that qualitatively similar results are obtained when we instead use a default prior for the effect size parameter
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