คำพูดแรกของเด็กดาวน์, and subsequent growth in early expressive vocabulary is slow compared with expectations for typically developing children (Berglund, Eriksson, & Johansson, 2001; Caselli et al., 1998; Mervis & Robinson, 2000). For example, only 12% of one year-old Swedish children with Down syndrome included in a large-scale survey study produced at least one word (Berglund et al., 2001). The prognosis for spoken language acquisition is good, however. Ninety percent of three year-olds and 94% of five year-olds produced one or more words (with 73% of five year-olds having 50 or more words).