Schachter and Singer (1962)

Chapter 2 endnote 15, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

In the 1960s, the psychologists Stanley Schachter and Jerome Singer famously injected test subjects with adrenaline ​— ​without the subjects’ knowledge ​— ​and saw them experience this mysterious arousal as anger or euphoria, depending on the context surrounding them.

The Schachter and Singer experiment, published in 1962, is one of the famous and controversial in the history of psychology. Some test subjects were secretly injected with adrenaline, giving them a sudden, unexplained surge of arousal. Subjects experienced this surge differently depending on context. Those subjects who were near someone acting happy (who was secretly part of the experiment) experienced the surge of arousal as euphoria, while subjects near someone acting angry experienced their surge as anger. Schachter and Singer concluded that people make meaning out of ambiguous changes in arousal, thereby constructing emotions.

Schachter and Singer (1962) is described in various ways in papers and textbooks, not all of which are altogether consistent. Sometimes this experiment is described as providing support for an appraisal view of emotion (which is a classical view emphasizing that cognitive interpretations cause emotions). Sometimes Schachter and Singer are described as having a "neo-peripheralistic" view (that arousal coming from the peripheral nervous system is necessary for emotion). Rarely is Schachter and Singer (1962) described as an example of a construction theory of emotion.

Schachter & Singer were not the first scientists to inject test subjects with adrenaline to examine the effect on emotion. Nevertheless, later experiments were not able to replicate the experimental results, and nowadays the study is infamous as an isolated moment in the history of emotion research.