A sexually abusive relationship is one over which a child or young woman has no control. A trusted family member or friend uses his power, as well as a child's love and dependence, to initiate sexual contact and often to ensure that the relationship continues and remains secret. The extent of incest and childhood sexual abuse is difficult to measure because of lack of reporting and lack of memory. One study in which adults were asked to report on past incidents found that one in four girls and one in ten boys experienced sexual abuse. Incest and sexual abuse of children take many forms and may include sexually suggestive language; prolonged kissing, looking, and petting; vaginal and/or anal intercourse; and oral sex. Because sexual contact is often achieved without overt physical force, there may be no obvious signs of physical harm.