The two-factor theory of emotion states that emotion is based on two factors: physiological arousal and cognitive label. The theory was created by researchers Stanley Schachter and Jerome E. Singer. According to the theory, when an emotion is felt, a physiological arousal occurs and the person uses the immediate environment to search for emotional cues to label the physiological arousal. This can sometimes cause misinterpretations of emotions based on the body's physiological state. When the brain does not know why it feels an emotion it relies on external stimulation for cues on how to label the emotion. Empirical support Stanley Schachter and Jerome E. Singer (1962) performed a study that tested how people use clues in their environment to explain physiological changes. Their hypotheses were: If a person experiences a state of arousal for which they have no immediate explanation, they will label this state and describe their feelings in terms of the cognitions available to them at the time. If a person experiences a state of arousal for which they have an appropriate explanation (e.g. 'I feel this way because I have just received an injection of adrenaline'), then they will be unlikely to label their feelings in terms of the alternative cognitions available. If a person is put in a situation, which in the past could have made them feel an emotion, they will react emotionally or experience emotions only if they are in a state of physiological arousal. Participants were told they were being injected with a new drug called "Suproxin" to test their eyesight. The participants were actually injected with epinephrine (which causes respiration, an increase in blood pressure and heart rate) or a placebo. There were four conditions that participants were randomly placed in: epinephrine informed, epinephrine ignorant, epinephrine misinformed, and a control group. The epinephrine informed group was told they may feel side effects including that their hands would start to shake, their heart will start to pound, and their face may get warm and flushed. In the epinephrine ignorant group, the experimenters did not explain to the subjects what symptoms they might feel. The epinephrine misinformed group was told that they would probably feel their feet go numb, and have an itching sensation over parts of their body, and a slight headache. The control group was injected with a placebo and was given no side effects to expect. This group was used as