Emotional expression propose that emotions are constructed based upon the person, situation, culture, and past experiences, and that there are no preset emotional responses that are consistent and specific to one emotion or another. The basic model of emotions finds its roots in Charles Darwin's "The Expression of Emotions in Man and Animals". Darwin claimed that the expression of emotions involves many systems: facial expression, behavioral response, and physical responses, which include physiological, postural, and vocal changes. Most importantly, Darwin claimed that emotional expression was consistent with his theories on evolution and thus, the expression of emotion is universal and should therefore
Emotion in animals could be used to include all the animal kingdom as well as some plants. The second approach, mechanistic, requires an examination of the mechanisms that drive emotions and search for similarities in animals. The mechanistic approach is utilized extensively by Paul, Harding and Mendl. Recognizing the difficulty in studying emotion in non-verbal animals, Paul et al. demonstrate possible ways to better examine this. Observing the mechanisms that function in human emotion expression, Paul et al. suggest that concentration on similar mechanisms in animals can provide clear insights into the animal experience. They noted that in humans, cognitive biases vary according