“…For example, but appears in the 3rd year in children's spontaneous speech [Bates, 1976;Bloom et al" 1980;French and Nelson, 1985], yet experimental studies find it to be a much later acquisition: age 9 in Hutson and Shub [1975] and 11-12 in Katz and Brent [ 1968]. Similarly, because appears in the 3rd year in children's spontaneous speech [Bloom et al, 1980], yet correct per formance with because occurs much later in experimental studies, though there is consid erable variation among their norms as well: 5-6 years in Emerson [1979] and some of the performances reported by Corrigan [1975], 7-8 years in Emerson and Gekoski [1980] and Kuhn and Phelps [1976], and 9-10 years or older in Bebout et al [1980], D'Arcais [1978], and Katz and Brent [1968].…”