The Two-Factor Theory of Emotion

Schachter and Singer's Theory of Emotion

Boy displaying his emotions
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What exactly makes up an emotion? According to one major theory of emotion, there are two key components: physical arousal and a cognitive label. In other words, the experience of emotion involves first having some kind of physiological response which the mind then identifies.

Cognitive theories of emotion began to emerge during the 1960s, as part of what is often referred to as the "cognitive revolution" in psychology.

One of the earliest cognitive theories of emotion was one proposed by Stanley Schachter and Jerome Singer, known as the two-factor theory of emotion.

What Is the Two-Factor Theory?

Like the James-Lange theory of emotion, Schachter and Singer felt that physical arousal played a primary in emotions. However, they suggested that this arousal was the same for a wide variety of emotions, so physical arousal alone could not be responsible for emotional responses.

The two-factor theory of emotion focuses on the interaction between physical arousal and how we cognitively label that arousal. In other words, simply feeling arousal is not enough; we also must identify the arousal in order to feel the emotion.

So, imagine you are alone in a dark parking lot walking toward your car. A strange man suddenly emerges from a nearby row of trees and rapidly approaches. The sequence that follows, according to the two-factor theory, would be much like this:

1. I see a strange man walking toward me.
2. My heart is racing and I am trembling.
3. My rapid heart rate and trembling are caused by fear.
4. I am frightened!

The process begins with the stimulus (the strange man), which is followed by the physical arousal (rapid heartbeat and trembling). Added to this is the cognitive label (associating the physical reactions to fear), which is immediately followed by the conscious experience of the emotion (fear).

The immediate environment plays an important role in how physical responses are identified and labeled. In the example above, the dark, lonely setting and the sudden presence of an ominous stranger contributes to the identification of the emotion as fear. What would happen if you were walking toward your car on a bright sunny day and an elderly woman began to approach you? Rather than feeling fear, you might interpret your physical response as something like curiosity or concern if the woman seemed to be in need of assistance. 

Schachter and Singer’s Experiment

In a 1962 experiment, Schachter and Singer put their theory to the test. A group of 184 male participants was injected with epinephrine, a hormone that produces arousal including increased heartbeat, trembling, and rapid breathing. All of the participants were told that they were being injected with a new drug to test their eyesight. However, one group of participants was informed the possible side-effects that the injection might cause while the other group of participants were not.

Participants were then placed in a room with another participant who was actually a confederate in the experiment. The confederate either acted in one of two ways: euphoric or angry. Participants who had not been informed about the effects of the injection were more likely to feel either happier or angrier than those who had been informed. Those who were in a room with the euphoric confederate were more likely to interpret the side effects of the drug as happiness, while those exposed to the angry confederate were more likely to interpret their feelings as anger.

Schacter and Singer had hypothesized that if people experienced an emotion for which they had no explanation, they would then label these feelings using their feelings at the moment. The results of the experiment suggested that participants who had no explanation for their feelings were more likely to be susceptible to the emotional influences of the confederate.

Criticism of Two-Factor Theory

While Schachter and Singer's research spawned a great deal of further research, their theory has also been subject to criticism. Other researchers have only partially supported the findings of the original study and have at times shown contradictory results. 

In replications by Marshall and Zimbardo, the researchers found that participants were no more likely to act euphoric when exposed to a euphoric confederate than when they were exposed to a neutral confederate. In another study by Maslach, hypnotic suggestion was used to induce arousal rather than injecting epinepherine. The results suggested that unexplained physical arousal was more likely to generate negative emotions no matter which type of confederate condition they were exposed to.

Other criticisms of the two-factor theory:

  • Sometimes emotions are experienced before we think about them.
  • Other researchers have supported James-Lange's initial suggestion that there are actual physiological differences between emotions.


Marshall, G., & Zimbardo, P. G. Affective consequences of inadequately explained physiological arousal. Journal of Personality and Social Psychology. 1979; 37: 970-988.

Maslach, C. Negative emotional biasing of unexplained arousal. Journal of Personality and Social Psychology. 1979; 37: 953–969. doi:10.1037/0022-3514.37.6.953.

Reisenzein, R. The Schachter theory of emotion: Two decades later. Psychological Bulletin. 1983; 94: 239-264.

Schachter, S. and Singer, J. E. Cognitive, social and physiological determinants of emotional states. Psychological Review. 1962; 69: 379-399

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