“…However, this view of L1 learning is simplistic. Although most children learn to communicate—that is, talk effectively, in their L1—there is normal variation not only in their rate of acquisition but also in their communication skills at every point in development, for example, size of vocabulary and complexity of sentence structures (Gilkerson et al, ; Hoff, , ; Huttenlocher, Waterfall, Vasilyeva, Vevea, & Hedges, ; Kidd, Donnelly, & Christiansen, ). In addition, individual differences (IDs) in L1 skills are large and stable across development (Bates, Dale, & Thal, ; Bornstein & Putnick, ).…”