Can standing like a superhero change your body, and why did the evidence fall apart?

The body part of the claim did not hold up; the feeling part may have. In 2010 Dana Carney, Amy Cuddy and Andy Yap suggested in Psychological Science that holding a powerful posture could change you. In their study, 42 participants were coached into a position of power, and the authors reported an increase in testosterone and a decrease in cortisol afterwards. Their takeaway was that in some situations requiring power, people can "fake it 'til they make it". Cuddy's 2012 TED talk made the idea famous, and by 2017 it had been viewed by about 47 million people.

Then the replications arrived. In 2015 a study with a larger sample confirmed the effect on felt power but could not detect any physiological or behavioural effects. A statistical review in 2016 concluded that the research did not suggest an effect once selective reporting was accounted for. That same year Carney, the first author of the original paper, said she no longer believed the effect was real. A 2017 special issue with eleven new studies and a meta-analysis found that the effect on power behaviours was not replicated.

The story did not end in a clean verdict. Cuddy continued her research, claiming evidence that posture can at least make people feel more powerful. A review of 128 published and unpublished studies found a reliable effect on thoughts and feelings, but none on physiological measures such as hormones or blood pressure. In other words, standing tall may lift mood, but the claim that it rewires your hormones did not survive.