Columbia psychology professors Stanley Schachter and Jerome Singer told subjects that they would be receiving an injection of “Suproxin,” a vitamin that could improve their visual skills. In reality, subjects received either saline or adrenaline.
Among those receiving adrenaline injections, half were informed of side effects (accelerated heart rate, etc.) or not informed.
Subjects were then placed in a waiting room in the company of an “subject” (really a researcher) who behaved either euphorically or angrily.
Those informed of side effects had a ready explanation of the reasons for the physiological arousal and reported no emotional response, as was the case for subjects who received saline (and experienced no arousal).
Those receiving adrenaline but no explanation for their arousal experienced it as emotions matched to the behavior of the other person in the waiting room.