Emotion is a very complex subject that has been discussed and researched for over 100 years. There are several definitions of emotion based upon the various theories that have developed over the course of that time period. However, a working definition of emotion that can be used is that emotions are the cognitive aspect of feeling or the value judgment placed on a particular experience.
Emotions have a physiological basis as was studied by Cannon who gave the first descriptions of bodily changes during simpler emotions and found that the thalamus is the center of emotion. The adrenal gland and adrenaline, acting along with the autonomic nervous system, produce the physiological changes within our bodies which we then label as emotions. (deCatanzaro 6) Papez identified the limbic system as being a critical part of many emotions. He argued that "emotions influence consciousness, and hence the cortex, and in turn higher cognitive functions influence emotions." (deCatanzaro 81) We label these physiological changes as emotions as stated in the James-Lange theory: "physiological changes occur during emotions, and our subjective experience of these emotions involves internal sensation of these changes." (deCatanzaro 8)
The relationship between emotion and cognition can be explained by theories of emotion developed by Zajonc, Leventhal, and Schacter. According to Zajonc, emotional responses can become socialized and that emotions can occur without cognition. He argued that emotions occur rapidly without any sentiment or thought.
Leventhal proposed a two phase model of emotion in that cognitions promote emotions and expressive reactions and that the overt action is separate from the instinctual. In order to express emotion, we must be able to attach a label to the physiological reactions that occur. Therefore the emotion that is actually presented differs from the instinctual response.
The most extensive theory detailing the relationship between emotion and cognition was developed by Schacter who suggested that "autonomic arousal was common to many emotions, and that cognitive and perceptual factors are required to differentiate among the emotions." (deCatanzaro 176-77) Emotions are primarily determined by cognition and arousal of the sympathetic nervous system. If an individual is physiologically aroused, the individual will label it and if that cognition is repeated, it will be labeled as an emotion.
There is another debate as to whether or not emotions are developed or if they are innate. Ekman conducted an experiment where he showed standardized pictures of human faces displaying specific emotions to subjects from diverse nations of the world and then measuring the percentage of instances in which they correctly identify the emotion. There was very high agreement across the cultures that were used in this experiment. This experiment has been replicated by a number of researchers who modified the experiment so that the participants would be asked to identify both primary and secondary emotions in the pictures of the facial expressions. They found that "although there are cultural differences in judgments of the intensity of emotional experience, agreement is very high across cultures regarding which emotion is most intensely expressed by facial features." (Ekman et al. 145)
In 1872, about one hundred years before Ekman conducted his experiment, Darwin proposed that emotions were "instinctive behavior patterns selected by pressures of natural selection." (deCatanzaro 32) In his studies, he found evidence of emotions in other animals which was consistent with his belief of continuity among species. He also suggested that differences in emotional expressions across cultures would be caused by inheritance not learning. Darwin's theory supports Ekman's findings in that Ekman's findings strongly suggest that emotional responses are innate and not learned.
Ekman's findings are consistent with the pleasure/pain response developed by McDougal. He stated that the primary emotions are the pleasure/pain emotions and that there are no cultural differences in experiencing primary emotions.
However, Campos suggests that emotions develop and are not innate. His experiment with human babies was designed to show whether or not parenting behavior affects emotion. Normally, babies at eight months old would display a fear of strangers; however, the babies whose mothers acted cheerful to the strangers, the babies' response to the strangers was affected accordingly. "The mother's expressive pose was found to significantly affect the infant's expressive behaviors, with infants showing much more smiling and motor activity when mothers posed joy, although heart rate was not significantly different." (deCatanzaro 297) Although these findings suggest that emotional response is learned, the actual physiological reaction is innate.
Campos's findings are consistent with the James-Lange theory in that emotions are based on experiences. Perception of the event is followed by the mental affective experience which in turn produces the emotional response. Because the infants witnessed a positive experience around strangers, they displayed positive emotional reactions.