Emotions are a tricky subject, both in life and in psychology. Questions like, why do you make me feel this way are not only confusing on a personal level, but also on a scientific level. First, let's distinguish emotions from feelings and moods. An emotion is an immediate specific positive or negative response to internal thoughts, or external environmental events. A feeling is the subjective experience of an emotion. It's what we refer to when we say things like, I feel angry, or I feel happy. A mood meanwhile is a diffuse, longer lasting emotional state that doesn't necessarily have an identifiable object or trigger. So if something frustrating happens to you, you might immediately feel the emotional response of anger, and for the next few days you might be in a bad mood. Let's move on to the various components of an emotion. So we know that emotions are immediate and specific responses. These responses have at least three parts, physiological, cognitive, and behavioral. A physiological component of an emotion might be bodily arousal, like a racing heart or tense muscles. The cognitive components of an emotion is the subjective conscious experience of emotion. And the behavioral components of an emotion is the characteristic overt expressions of the emotion. Behavior is that other people can read, like particular facial expressions or posture. Charles Darwin studied this third component of emotions in his 1872 book, The Expression of Emotions in Man and Animals. In which he argued that particular emotional responses tend to accompany the same emotional states in all members of a species. So according to Darwin's argument, all of the members of a species will display the same behavior when they feel a particular emotion. All cats will display the same behavior when they are happy. And all humans will have the same facial expression and behavior when scared. But this evidence, Darwin suggested that the expression of emotion is genetically determined. This behavior has evolved and has been passed down through generations in our genes. Now let's look at some theories of how emotions work. Let's start with the common sense view. In this view, a stimulus prompts an emotion which in turn prompts some bodily arousal. So in this case, a frightening spectacle fills our villain with fear, which makes him sweat and makes his heart rate rise. In the mid-1880s, two scholars William James and Carl Lang independently came up with similar theories that contradicted this common sense view. James and Lang both suggested that instead of emotions causing bodily arousal, bodily arousal causes emotions. So to return to our previous example, that would mean that the sight of the hero on his threshold makes our villain's heart beat faster, his hands tremble and his palms sweat. And these physiological changes cause him to feel fear. But this theory is vulnerable to a few criticisms. First it is possible to have physiological arousal without any accompanied emotion. For instance, your palms might sweat because it's hot, but that sweat won't make you feel nervous, just kind of gross. Second, physiological changes can be too slow to proceed the conscious experience of emotion. Our villain might feel scared as soon as he sees our hero, but it might take a few seconds for him to start sweating. Third, the same set of physiological responses are associated with very different emotional experiences. A faster heart rate could mean fear, but it could also mean anger, or surprise, or joy. Finally, there is evidence that physiological feedback is not necessary for emotion. For example, patients with spinal cord injuries who have lost most of their physiological feedback still experience the same emotions as before. However, in the James Lang theory's favor, there is notably some slight evidence of dissipation in their emotional reactions. As an alternative to the James Lang theory, two other theorists, Walter Kennan and Philip Bard, propose that the physiological arousal of emotions and the experience of emotions are entirely separate processes. It is, a stimulus causes the emotion and physiological arousal independently. Neither one causes the other. So the sight of our hero causes our villain, both to feel fear and for his palms to sweat and hurt to race. But contrary to this theory, there have been many reports of physiological stimuli influencing emotions. So, it's unlikely that physiology and emotions are completely disconnected. One suggestion of how arousal and the experience of emotion may be connected, but not causal, was proposed in the 1960s by Stanley Schachter and Jerome Singer, as the Schachter Singer II factor theory, which introduces the factor of cognition. The theory suggests that when a stimulus elicits some arousal, this arousal elicits some cognition, which interprets the source of the arousal, and then this interpretation then elicits the experience of emotion. From the stimulus, it takes two different factors, the arousal and the cognition, two elicits the emotion, hence the name Schachter Singer II factor theory. For example, say that you feel your face start to flush. According to this theory, you'll automatically use cues from your environment to help explain this flush. You might be in a mid workout, or someone might have just confessed their love to you. Although the arousal is the same, the cognitive evaluation of the stimulus is very different across these two scenarios. And so the emotions you would feel would also be very different. Say pride versus shyness, for instance. To return to our previous example, if the sight of our hero makes our villains heartbeat faster, then their cognitive evaluation of the situation, say remembering that the hero was a secret service agent, here to save the world, or that he is their long-lost love from primary school, will determine their emotional response to the situation. Again, with this theory, it's about the interpretation of the stimuli in the arousal, which leads to the emotion. So let's just quickly review these four theories of emotion to help you remember them. First, the common sense view is that a stimulus will cause an emotion, which causes arousal. Second, the James Lang theory reverses emotion and arousal, suggesting instead that a stimulus causes arousal, which then causes emotion. Third, the canon bar theory separates out emotion and arousal as independent reactions to the stimulus. And finally, the Schachter-Singer 2-Factor theory adds another factor to the cause of emotion. After a stimulus elicits some arousal, you cognitively assess the stimulus, and that assessment causes the emotion.