Posture causes mood: Evidence

Posture affects your mood, and your mood affects your posture. Or to put it another way your body affects your mind and your mind affects your body. As I talked about before, this feedback relationship is fundamental to tai chi, and now I can point out some decent research to back that up (and another write up here).

Published in the Psychological Science, Cuddy and coauthors Dana R. Carney and Andy J. Yap performed this experiment:

"Subjects in the high-power group were manipulated into two expansive poses for one minute each: first, the classic feet on desk, hands behind head; then, standing and leaning on one's hands over a desk. Those in the low-power group were posed for the time period in two restrictive poses: sitting in a chair with arms held close and hands folded, and standing with arms and legs crossed tightly. Saliva samples taken before and after the posing measured testosterone and cortisol levels. To evaluate risk tolerance, participants were given $2 and told they could roll a die for even odds of winning $4. Finally, participants were asked to indicate how 'powerful"' and 'in charge' they felt on a scale from one to four."

The results indicated:

Controlling for subjects' baseline levels of both hormones, Cuddy and her coauthors found that high-power poses decreased cortisol by about 25 percent and increased testosterone by about 19 percent for both men and women. In contrast, low-power poses increased cortisol about 17 percent and decreased testosterone about 10 percent.
Not surprisingly, high-power posers of both sexes also reported greater feelings of being powerful and in charge. In addition, those in the high-power group were more likely to take the risk of gambling their $2; 86 percent rolled the die in the high-power group as opposed to 60 percent of the low-power posers.
Previous research established that situational role changes can cause shifts in hormone levels. In primate groups, for example, after an alpha male dies the testosterone levels of the animal replacing him go up. The hormonal shifts measured in this experiment show that such changes can be influenced independent of role, situation, or any consciously focused thoughts about power. The physical poses are enough.

As this much more detailed article underlines, the implications are simply that if you want to affect your mood, it is sufficient to change your posture. Or simply "fake it until you make it". So to extrapolate into tai chi terms, if you relax your body your mind will follow.