Or, as Boing Boing put it, “Hulk Smash Puny Placebo Effect!”:
Women who thought they were getting a dose of testosterone behaved more aggressively and selfishly–whether or not they’d really been given the hormone. Women who got testosterone and didn’t know it were actually more altruistic. The researchers suspect macho testosterone lore created a “license to misbehave” in the women who thought they were under its influence.
For a fuller discussion, see here. The author of the study concludes:
“Whereas other animals may be predominantly under the influence of biological factors such as hormones, biology seems to exert less control over human behaviour. Our findings also teach an important methodological lesson for future studies: it is crucial to control for subjects’ beliefs because the [effect of a pure substance] may be otherwise under- or overestimated.”
(Thanks, Mr Jender!)