In contrast to nursery rhymes, which are learned in childhood and passed from adults to children only after a gap of 20 to 40 years, children's playground and street songs, like much children's lore, are learned and passed on almost immediately.[15] The Opies noted that this had two important effects: the rapid transmission of new and adjusted versions of songs, which could cover a country like Great Britain in perhaps a month by exclusively oral transmission, and the process of "wear and repair", in which songs were changed, modified and fixed as words and phrases were forgotten, misunderstood or updated.[16]