and of the differences between private and public behaviors. For some children, genital touching increases, especially when they are tired or upset. Early school age covers approximately ages five to seven, and masturbation is common at these ages. Children become more aware of gender differences, and tend to choose same-sex friends and playmates, even disparaging the opposite sex. Children may drop their close attachment to their opposite-sex parent and become more attached to their same-sex parent. During this time, children, especially girls, show increased awareness of social norms regarding sex, nudity, and privacy. Children may use sexual terms to test adult reaction. "Bathroom humor" (jokes and conversation relating to excretory functions), present in earlier stages, continues. "Middle childhood" covers the ages from about six to eleven; depending on the methodology and the behavior being studied, individual development varies considerably. As this stage progresses, the choices of children picking same-sex friends becomes more marked and extending to disparagement of the opposite sex. By the age of 8 or 9 children become aware that sexual arousal is a specific type of erotic sensation and will seek these pleasurable experiences through various sights, self-touches, and fantasy. Although there are variations between individual children, children are generally curious about their bodies and those of others, and explore their bodies through explorative sex play. "Playing doctor" is one example of such childhood exploration; such games are generally considered to be normal in young children. Child sexuality is considered fundamentally different from adult sexual behavior, which is more goal-driven. Among children, genital penetration and oral-genital contact are very uncommon, and may be perceived as imitations of adult behaviors. Such behaviors are more common among children who have been sexually abused. A 1997 study based on limited variables found no correlation between early childhood (age 6 and under) peer sexual play and later adjustment. The study notes that its results do not demonstrate conclusively that no such correlation exists. The study also does not address the question of consequences of intense sexual experiences or aggressive or unwanted experiences. Childcare In childcare settings outside the home there is difficulty in determining what behavior is normal and what may be indicative of child sexual abuse (CSA). In 2018 an extensive study of Danish childcare institutions (which had, in the prior century, been tolerant of child nudity and playing doctor) found that contemporary policy had become restrictive as the result