Nudity is one of the physiological characteristics of humans, who alone among primates evolved to be effectively hairless. Human sexuality includes the physiological, psychological, and social aspects of sexual feelings and behaviors. In many societies, a strong link between nudity and sexuality is taken for granted. Other societies maintain their traditional practices of being completely or partially naked in social as well as private situations, such as going to a beach or spa. The meaning of nudity and sexuality remains ambivalent, often leading to cultural misunderstandings and psychological problems.