Two-factor theory of emotion

The two-factor theory of emotion, or Schachter–Singer theory, states that emotion is a function of both cognitive factors and physiological arousal. According to the theory, "people search the immediate environment for emotionally relevant cues to label and interpret unexplained physiological arousal."

Schachter and Singer study
Stanley Schachter and Jerome E. Singer (1962) performed a study on 184 college students on how emotion results from a state of arousal and what makes the best explanation of the situation. They designed a study as follows: they would give the participants an injection of epinephrine (adrenaline), although all participants were told that they were given a new drug called "Suproxin" to test their eyesight. Shortly after an injection of adrenaline typically blood pressure and heart rate both increase, blood flow increases, while muscle and cerebral blood flow increase, blood sugar and lactic acid concentration increases, and respiration rate increases slightly. Schachter and Singer then manipulated the participants giving them cues which placed them on one of four groups: epinephrine informed, epinephrine ignorant, epinephrine misinformed, and placebo.

Procedure
Epinephrine informed: The experimenters would tell the participates that some subjects had experienced side effects from the "Suproxin" and that those side effects would last for about 15–20 minutes. Subjects were told their hands would start to shake, their heart will start to pound, and their face may get warm and flushed. Once again, they would mention that the effects would last 15–20 minutes. While the physician was giving the injection, subjects were told that the injection was mild and harmless but the physician repeated the description of the symptoms that the subject could expect. Therefore, the subjects would know precisely what they would probably feel from an injection of epinephrine and why.

Epinephrine ignorant: The experimenter said nothing relevant to the side effects and left the room while the physician was giving the injection. The physician again told the subject that the injection was mild and harmless but said it would have no side effects. In this group, the experimenters didn't explain to the subjects what symptoms of effects of epinephrine they might feel.

Epinephrine misinformed: In this group, the experimenter would misinform the subjects about what they would feel. The experimenter again told them the side effects would only last around 15–20 minutes, but they were told they would probably feel their feet go numb, and have an itching sensation over parts of their body, and a slight headache.

All of those subjects were injected with the same dose of epinephrine. (When there was a placebo condition, the subjects were injected with saline solution.  Those injected with the saline solution, were given the same treatment as the epinephrine conditions.) None of these symptoms in the misinformed group are consequences of an injection of epinephrine.

After the physician left the room, an actor came into the room. The actor was to manipulate the situation by acting euphoric or angry. To demonstrate these emotions, the actor had a specified routine of verbal, nonverbal, and actions to perform. For the euphoria routine, as soon as the experimenter left the actor introduced himself, made a series of icebreaker comments and then started the routine.

The anger actor did not break the ice. As the subjects were filling out a five page questionnaire, the actor paced his or her own answers with the subjects. At several points in during the questionnaire, the actor made comments about the questions. His comments started off innocently, then grew angry, and the actor ended up in an apparent rage.

To record evidence of euphoria or anger, an observer kept a chronicle of what the subjects did and said. For the euphoria stage, there were four specific categories the observers looked for: 1) the subject joins the stooge’s activity,2) subject initiates a new activity, 3) subject ignores the stooge, or 4)subject  simply watches the stooge. During any particular behavior, the subjects were was coded in one or more of these categories.

There were six categories of measurement during the anger stage. The observer would record the subjects in the following categories: 1) the subject agrees with the stooge, 2)the subject disagrees with the stooge, 3) the subject is neutral or has a noncommittal response, 4) the subject initiates agreement or disagreement, 5) the subject watches without comment, and 6) the subject ignores the stooge.

Results
Singer and Schachter checked the results of the injections and the bodily state. Singer and Schachter asked themselves a single question, "do the injections of epinephrine produce symptoms of sympathetic nervous system (SNS) discharge as compared to the placebo injections?" In Singer and Schachter's results, the epinephrine group showed more SNS activation than the group which received the placebo: the pulse rate of the epinephrine subjects had increase tremendously compared to the placebo (whose pulse rates decreased.)

The results showed all their possible comparisons on the symptoms, mean scores of the epinephrine conditions were significantly greater than the corresponding scores in the placebo (P < .001). Singer and Schachter's examination of the two groups of subjects showed that epinephrine subjects were indeed in a state of physiological arousal, while the placebo subjects were in an normal or non aroused physiological state.

Effects of the manipulation on the emotional state were both significantly observable. Singer and Schachter believed that different results in the epinephrine misinformed vs epinephrine informed groups makes it clear that the experimental differences in SNS arousal are not an artifact of expectations. (With a few subjects the epinephrine did not have any effect at all. Those subjects did not report any tremors, showed no increase in pulse, and did not have any other relevant physical symptoms.)

It was clear from the study that cues had a strong effect on euphoria. There was consistent pattern that epinephrine misinformed and ignorant subjects were the most euphoric. They were more euphoric than the placebo subjects and the epinephrine informed subjects. The research concluded that subjects can be manipulated into states of euphoria, anger, or amusement. If a subject has a state of physiological arousal with no explanation he will label this state due to the cues available to him. Therefore, this means that by manipulating the cues available to an aroused subject, his or her emotional responses can be manipulated.

Summary
When an individual has no immediate explanation for the state of physiological arousal they are feeling, they will label the feelings based on cues that are available to them. That is why subjects have feelings of either euphoria or anger when they had unexplained SNS arousal. The subjects that were in the misinformed or ignorant condition behaved similarly to the stooge, while those who were correctly informed of the expected SNS responses, had little to no mirroring of the actor's cues. They concluded that when the subjects were informed of the reason for the SNS arousal, they had a perfectly appropriate explanation for this and did not have a need to find an external basis for these feelings.

The results support the proposition that following the injection of epinephrine, some subjects had no explanation for the bodily state they felt. They did give behavioral and self-report indications that they had been manipulated into the feeling states of euphoria and anger. Subjects' emotional states were inferred from both observations of the subjects and the subjects responses on a self-rating of emotion scale. Those subjects who had received the adrenaline injection were more emotional by both measures, showing that the first factor in emotion, intensity, resulted from visceral arousal.

Participants who were in the misinformed or ignorant condition behaved similarly to the actor, while those who were informed of the expected effects of the adrenaline showed no emotional pattern. This suggests that participants who were informed cognitively attributed their feelings to the physiological effects of the adrenaline, while the uninformed or misinformed groups could perform no such attribution and so interpreted the feelings as emotion. Schachter's cognitive labeling theory thus identifies "cognitive attribution," the mind's attempt to pair the feeling of arousal with its (inferred) causal pattern in the environment as the second factor in the Two-factor Theory of Emotion.

Misattribution of arousal
The misattribution of arousal study tested the two-factor theory of emotion. This theory has helped support Schachter & Singer’s concept of the two-factor theory. Psychologists Donald G. Dutton and Arthur P. Aron wanted to use a natural setting that would induce physiological arousal. In this experiment, they had male participants walk across two different styles of bridges. One bridge was a very scary (arousing) suspension bridge, which was very narrow and suspended above a deep ravine. The second bridge was much safer and more stable than the first.

At the end of each bridge an attractive female experimenter met the participants. She gave the participants a survey to fill out and a number to call if they had any other further questions. The idea of this study was to find which group of males were more likely to call the female experimenter. The results found that the men who walked across the scary bridge were most likely to call the woman, asking for a date. This was most likely due to the arousal they felt from walking across the scary bridge. They had misattributed their arousal from the bridge towards the woman, making her seem more attractive. Strangely, when asking the males why they called the woman they all had reasons for why they called her. Some said it was because of her attractive face, body, and eyes. Yet, none of the participants attributed their feelings to the bridge causing arousal, therefore causing the experimenter to become more attractive.

Supporting evidence
In the Schachter & Wheeler (1962) study the subjects were injected with epinephrine, chlorpromazine, or a placebo. Chlorpromazine is similar form of a tranquilizer. None of the subjects had any information about the injection. After receiving the injection, the subjects watched a short comical movie. While watching the movie, the subjects were monitored for signs of humor. After the movie was watched, the subjects rated how funny the movie was and if they enjoyed. The results concluded that the epinephrine subjects demonstrated the most signs of humor. The placebo subjects demonstrated fewer reactions of humor but more than the chlorpromazine subjects.

Erdmann & Janke (1978) administrated their subjects with ephedrine, adrenaline like substance or they were give a placebo. The administrators informed the subjects that they were testing the comparison between pills and powders. Therefore, the subjects were not aware they had taken a drug. After the drug was taken, the subjects followed one of four different routes: neutral, happy, anger, or anxiety conditions. For the neutral condition the subjects rated a text on the nature of the experiment. For the happy conditions subjects were reminded that they had done very well on an earlier mock intelligence test. Then they were asked several complimentary questions, such as: how many grades had they skipped in school? In the anger conditions subjects it was the exact opposite. They were told how horrible they had done on a previous intelligence examination, and were asked how many times they had to repeat a grade in school. While for the subjects in the anxiety conditions, subjects were told they would be receiving electric shocks and were given several mild shocks. The result found that both physiological and self reported data showed that the drug increased the subject’s arousal levels over the placebo effect. Data from the mood scale showed that drug manipulation increased the angry and happy conditions, although the happy subjects felt much happier than the anger condition subjects.

Criticism of the theory
Criticism of the theory has come from attempted replications of the Schachter and Singer (1962) study. Marshall and Zimbardo (1979, and Marshall 1976) tried to replicate the Schachter and Singer’s euphoria conditions. Just as Schachter and Singer did, the subjects were injected with epinephrine or a placebo, except the administrator told the subjects that they will be experiencing non-arousal symptoms. Then the subjects were put into four different conditions: subjects injected epinephrine and were exposed to a neutral confederate, another in which they received the placebo and were told to expect arousal symptoms, and two conditions in which the dosage of epinephrine was determined by body weight rather than being fixed. The results found that euphoria confederate had little impact on the subjects. Also, that the euphoric confederate didn’t produce any more euphoria than the neutral confederate did. Concluding that the subjects who were injected with epinephrine were not more susceptible to emotional manipulations than the non-aroused placebo subjects.

Maslach (1979) designed a study to try to replicate and extend on the Schachter and Singer study. Instead of being injected with epinephrine, the administrators used hypnotic suggestions for the source of arousal. Either the subjects were hypnotized or were used as a control (same as the placebo effect in the Schachter and Singer study). Subjects that were hypnotized were given a suggestion to become aroused at the presentation of a cue and were instructed not to remember the source of this arousal. Right after the subjects had been hypnotized, a confederate began acting either in a euphoric or angry condition. Later on in the study the subjects were exposed to two more euphoric confederates. One confederate was to keep aware the source of the arousal, while the other confederates told the subjects to expect different arousal symptoms. The results found that all the subjects both on self-reports and on observation found that unexplained arousal causes negative conditions. Subjects still showed angry emotions regardless of the euphoric confederate. Maslach concluded that when there is a lack of explanation for an arousal it will cause a negative emotion, which will evoke either anger or fear. However, Maslach did mention a limitation that there might have been more negative emotion self-reported because there are more terms referring to negative emotions than to positive ones.