Emotional states often result in characteristic changes in a person's physical appearance or in the sound of their voice. Similarly, fear, joy, aggression, timidity, sadness and other emotions appear to produce reliable changes in the human voice. For social animals, like humans, deciphering the emotional states of others is important. Emotional expressions can be used to deceive others. For example, a person might feign love, or pretend to be angry, in order to achieve a particular benefit.
Humans appear to be very sensitive to possible deception in emotional expressions.
Emotions are widely viewed as essential to living a meaningful and fully human life.