Prof Panda is being a bit harsh here. Replications have been mixed. Cuddy and colleagues have studied how nonverbal expressions of power, such as expansive postures affect behaviour and hormone levels. Subjective reports of perceived personal power tend to be more affected than computational tasks or measures of hormones. Social psychology studies are going through a bit of a crisis at the moment, with new studies often unable to replicate previously seen effects. Whether the power pose will be further reinforced or undermined by new experiments remains to be seen.
Here is Amy Cuddy’s video about power poses on TED.
Prof Panda: Why are you teaching her that?
Dr Mad: This is a power pose! Standing like this modifies your behaviour!
Prof Panda: That was disproven recently. New experiments cannot replicate the effect.
Dr Mad: Nah, it just didn't work for increasing confidence. The main behaviour this modifies is EVILNESS!
Dr Mad: Give it a try!
Prof Panda: Hmph.
FX: CRACK BOOM
Prof Panda: MWAHAHAHA!!
Prof Panda: I don't feel it.