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 as when rolling and rubbing. Therefore, purring can be generally considered as an indicator of "pleasure" in cats. Low pitched bleating in sheep has been associated with some positive-valence situations, as they are produced by males as an estrus female is approaching or by lactating mothers while licking and nursing their lambs. The argument that animals experience emotions is sometimes rejected due to a lack of evidence, and those who don't believe in the idea of animal intelligence, often argue that anthropomorphism plays a role in individuals' perspectives. Those who reject that animals have the capacity to experience emotion do