More than a century ago, in the 1870s, Charles Darwin proposed that emotions evolved because they had adaptive value. For example, fear evolved because it helped people to act in ways that enhanced their chances of survival. Darwin believed that facial expressions of emotion are innate (hard-wired). He pointed out that facial expressions allow people to quickly judge someoneís hostility or friendliness and to communicate intentions to others.

Recent evolutionary theories of emotion also consider emotions to be innate responses to stimuli. Evolutionary theorists tend to downplay the influence of thought and learning on emotion, although they acknowledge that both can have an effect. Evolutionary theorists believe that all human cultures share several primary emotions, including happiness, contempt, surprise, disgust, anger, fear, and sadness. They believe that all other emotions result from blends and different intensities of these primary emotions. For example, terror is a more intense form of the primary emotion of fear.

Walter B. Cannon, a Harvard physiologist, questioned the James-Lange theory on the basis of a number of observations; he noted that the feedback from bodily changes can be eliminated without eliminating emotion; that the bodily changes associated with many quite different emotional states are similar, making it unlikely that these changes serve to produce particular emotions; that the organs supposedly providing the feedback to the brain concerning these bodily changes are not very sensitive; and that these bodily changes occur too slowly to account for experienced emotions.

Cannon and a colleague, Philip Bard, proposed an alternative arousal theory, subsequently known as the Cannon-Bard theory. According to this approach, the experience of an event, such as the automobile accident mentioned earlier, leads to the simultaneous determination of emotion and changes to the body. The brain, upon receiving information from the senses, interprets an event as emotional while at the same time preparing the body to deal with the new situation. Thus, emotional responses and changes in the body are proposed to be preparations for dealing with a potentially dangerous emergency situation.

In 1927, Cannon published a landmark paper critiquing the James-Lange theory and suggesting an alternate approach to understanding emotions. According to Cannon, scientific evidence suggested that there were several problems with the James-Lange theory:

The Theory

Event ==> Simultaneous Arousal and Emotion

The above sequence summarizes the Cannon-Bard Theory of Emotion. In essence, the theory is backed up by neurobiological science. In a stimulating event, sensory signals are transmitted to the brainís relay center, the thalamus. Once the thalamus receives the signal, it relays the information to two structures: the amygdala and the brain cortex. The amygdala is responsible for the instantaneous response in the form of emotions, whereas the brain cortex is for the slower response. At the same time, the autonomic nervous system or ANS sends signals to muscles and other parts of the body, causing them to tense, increase in rate, change in rhythm, and more. Therefore, this theory views stimulation/arousal and emotion as a combined response to a stimulating event.

For instance, when a person sees a venomous snake, he feels afraid and his muscles get tensed at the same time, preparing to run away from the dangerous animal. One can observe the personís emotion based on the physiological signals that his body displays.

Examples of Cannon-Bard

Cannon-Bard can be applied to any event or experience that causes an emotional reaction. The emotion can be positive or negative. The scenarios described below show how this theory is applied to real-life situations. In all these scenarios, the Cannon-Bard theory states the physical and emotional reactions happen simultaneously, rather than one causing the other.

A job interview

Many people find job interviews stressful. Imagine you have a job interview tomorrow morning for a position you really want. Thinking about the interview might leave you feeling nervous or worried. You might also feel physical sensations such as tremors, tense muscles, or a rapid heartbeat, especially as the interview approaches.

Moving into a new home

For many people, moving into a new home is a source of happiness and excitement. Imagine youíve just moved into a new home with your partner or spouse. Your new home is larger than the apartment you lived in before. It has enough space for the children you hope to have together. As you unpack boxes, you feel happy. Tears well in your eyes. Your chest is tight, and itís almost difficult to breathe.

Divorce of parents

Children also experience physical and emotional effects in response to significant events. An example is the separation or divorce of their parents. Imagine youíre 8 years old. Your parents just told you that theyíre separating and will probably get a divorce. You feel sad and angry. Your stomach is upset. You think you might be sick.

Criticisms of James-lange Theory

As mentioned, the theory by Cannon and Bard emerged from their refutation of the concepts under the James-Lange Theory. Based on their experiments, the theorists came up with seven concepts that negate the James-Lange Theory. These include:

1.     No alteration on emotional behaviour occurs when the viscera is totally separated from the central nervous system or CNS. This was proven by the cats being alive after the viscera have been removed.

2.     Various emotional and non-emotional (purely physiologic) states emerge as a result of similar visceral changes. For instance, increased heart rate may not only indicate fear, but may also be a sign of high fever.

3.     The components of the viscera are found to be reasonably insensitive parts of the body.

4.     Emotions and feelings may not result from visceral changes simply because visceral changes occur too slowly.

5.     Strong emotions that are typically attributed to specific visceral changes may not be produced if the same visceral changes are triggered through artificial means.

6.     The action of the subcortical centers of the brain leads to emotional expression.

7.     Affective experience results from thalamic responses.