Little is known about the actual cause of nocturnal emissions, leaving explanation of the phenomenon to wide speculation. Popular claims include stimulation of genitals by a mattress or sheets, erotic dreams, or memories of sexual activity or thoughts. However research has shown no conclusive connection between masturbation frequency and nocturnal emissions (see Frequency below) nor has it shown that erotic thoughts or dreams accompany nocturnal emissions. Although these causes have not been conclusively ruled out, they also have not been substantiated by experiment; currently, what can be agreed upon is they begin only after puberty due to increased testosterone production. (wikipedia)