A facial expression is one or more motions or positions of the muscles beneath the skin of the face. These movements convey the emotional state of an individual to observers. Facial expressions are a form of nonverbal communication. They are a primary means of conveying social information between humans, but they also occur in most other mammals and some other animal species.
Humans can adopt a facial expression voluntarily or involuntarily, and the neural mechanisms responsible for controlling the expression differ in each case. Voluntary facial expressions are often socially conditioned and follow a cortical route in the brain. Conversely, involuntary facial expressions are believed to be innate and follow a subcortical route in the brain.
Human behavior refers to the range of behaviors exhibited by humans and which are influenced by culture, attitudes, emotions, values, ethics, authority, rapport, hypnosis, persuasion, coercion and/or genetics.
The behavior of people (and other organisms or even mechanisms) falls within a range with some behavior being common, some unusual, some acceptable, and some outside acceptable limits. In sociology, behavior in general is characterised as having no meaning, being not directed at other people, and thus is the most basic human action. Behavior in this general sense should not be mistaken with social behavior, which is a more advanced action, as social behavior is behavior specifically directed at other people. The acceptability of behavior depends heavily upon social norms and is regulated by various means of social control. Human behavior is studied by the specialised academic disciplines of psychiatry, psychology, social work, sociology, economics, and anthropology.
Sexual attraction is attraction on the basis of sexual desire or the quality of arousing such interest. Sexual attractiveness or sex appeal refers to an individual's ability to attract the sexual or erotic interest of another person, and is a factor in sexual selection or mate choice. The attraction can be to the physical or other qualities or traits of a person, or to such qualities in the context in which they appear. The attraction may be to a person's looks or movements or to their voice or smell, besides other factors. The attraction may be enhanced by a person's adornments, clothing, perfume, hair length and style, and anything else which can attract the sexual interest of another person. It can also be influenced by individual genetic, psychological, or cultural factors, or to other, more amorphous qualities of the person. Sexual attraction is also a response to another person that depends on a combination of the person possessing the traits and also on the criteria of the person who is attracted.
Though attempts have been made to devise objective criteria of sexual attractiveness, and measure it as one of several bodily forms of capital asset (see erotic capital), a person's sexual attractiveness is to a large extent a subjective measure dependent on another person's interest, perception, and sexual orientation. For example, a gay or lesbian person would typically find a person of the same sex to be more attractive than one of the other sex. A bisexual person would find either sex to be attractive. Asexuality refers to those who do not experience sexual attraction for either sex, though they may have romantic attraction (homoromantic, biromantic or heteroromantic). Interpersonal attraction includes factors such as physical or psychological similarity, familiarity, similarity, complementarity, reciprocal liking, and reinforcement.
Philosophy of love is the field of social philosophy and ethics that attempts to explain the nature of love. The philosophical investigation of love includes the tasks of distinguishing between the various kinds of personal love, asking if and how love is or can be justified, asking what the value of love is, and what impact love has on the autonomy of both the lover and the beloved.