This is the 2007 version. Click here for the 2017 chapter 09 table of contents.

Evolutionary Theories

An early attempt to describe and explain emotion was Darwin's The Expression of the Emotions in Man and Animals (1872). Darwin argued that animal emotion had two important evolutionary functions:

1. Emotion communicates to other animals. For example, an emotional display may indicate an intention to fight.

What functions did Darwin see for emotion, and how was this illustrated by his example of the fierce cat?

2. Emotion prepares animals for action. For example, anger is accompanied by tense muscles.

This following figure is from Darwin's book on emotions of animals and humans. The cat-arching its back, erecting its hair, and showing its teeth-warns another animal of a possible attack. It also makes itself look fiercer and larger. To Darwin this was a clear example of an instinctive display of emotion.

Darwin's drawing of a cat recoiling from a threatening dog

Darwin felt that humans also used instinctive ways of expressing emotion with facial expression. To test this idea, Darwin selected pictures showing various emotions and showed them to 20 people. There was unanimous agreement about the emotion shown in some pictures, but not all, so he concluded that some emotions were universal, others were specific to one culture. Darwin's speculations foreshadowed the systematic work of Ekman, described later in this chapter.

Evolutionary theories emphasize the instinctive nature of emotional response. That idea has re-emerged in the modern distinction between two different learning pathways into the brain, the "heart vs. head" distinction from Chapter 3.

One circuit, represented by the hippocampus and frontal lobes, is involved in conscious decision making, event memories, and intellectual control. It is also related to the "cool" motivational system described earlier in this chapter. It occurred more recently in evolution.

The other circuit, involving "the heart," is the circuit activating the amygdala and other structures of the limbic system. It is involved in avoidance conditioning, impulsive appetities, and conditional emotional responses. It tends to involve unconscious, emotional experiences, and it relates to the "hot" motivational system described earlier.

Normally the two circuits work together, but they can be dissociated by brain injury, and one (the emotional circuit) is evolutionarily older than the other. Emotions are not always subject to intellectual control. This is one reason psychotherapy often involves getting rid of bad emotional responses—something a person cannot necessarily do using willpower alone.

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Copyright © 2007-2011 Russ Dewey