The Homosexual Matrix the most novel account of the way in which behavioral expression communicates internal states since Charles Darwin's "The Expression of the Emotions in Man and Animals" (1872), but considered his most original contribution to be his explanation of how erotic feeling depends on "resistance", which might consist of any of several impediments to easy access to sexual satisfaction. Begelman called Tripp a skillful writer who was learned on the subject of homosexuality, but whose objectivity was nevertheless open to question. Karlen wrote that Tripp made numerous unjustified claims, such as that homosexual men tend to have a larger than average
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