Promoting Generalization and Maintenance of Skills Learned Via Natural Language Teaching

Introduction Delays in language acquisition can have serious deleterious effects on the educational and social development of children (Goldstein & Kaczmarek, 1992; Ramey & Campbell, 1992; Warren & Kaiser, 1986). Such delays are considered by some to be a "developmental disaster" (Warren & Kaiser, 1986). Unfortunately, delayed language acquisition is one of the most prevalent disabilities in early childhood. For example, Wetherby and Prizant (1992) reported that 70% of 3- to 5-year-olds with developmental disabilities have language delays (Wetherby & Prizant, 1992). The influence of various environmental factors on children's language development has been clearly established over the last 20 years (e.g., Bricker, 1993; Hart & Risley, 1992, 1995; Moerk, 1986, 1992; Walker, Greenwood, Hart, & Carta, 1994); and children with developmental disabilities are known to be especially vulnerable to these variables (Tannock & Girolametto, 1992). These variables include, for example, the caregiver's responsiveness to child vocalizations, the reciprocity in verbal interaction between caregiver and child, the frequency of verbal interaction, and the availability of stimulating materials (Bradley & Caldwell, 1976; Hart & Risley, 1992; Huttonlocher, Haight, Bryk, Seltzer, & Lyons, 1991). Of the environmental factors that influence language development, patterns of child-addressed speech have surfaced as particularly important (Hart, 1991; Hemmeter & Kaiser, 1990; Warren & Kaiser, 1988). For this reason, caregivers are considered to have a "critical influence on the child and the child's language learning environment" (Hemmeter & Kaiser, 1990, p. 335); and patterns of child addressed speech have been observed to either support or limit language learning opportunities (Nelson, 1973). For example, Hart and Risley (1995) reported differences between parents in both the quantity and quality of child-addressed speech. Moreover, they found that the style of parental responsiveness, feedback tone, and guidance was positively correlated with language growth. More specifically, the children of families from higher SES groups heard an average of 2,150 words per hour in comparison to the children families from lower SES group, who heard only 620 words per hour (Hart & Risley, 1995, p. 132). Further, the language addressed to the children in the higher SES group included a richer distribution of particular linguistic features (e.g., nouns, modifiers, past-tense verbs, auxiliary-fronted questions, declarative sentences, and multi-clause sentences) and a more positive pattern of messages (e.g., a higher frequency of positive feedback. fewer imperatives, less negative feedback). As expected, by age three years, the vocabularies of the children who were provided with this richer and more positive language style were two times larger than the vocabularies of the children whose language input was more restricted and less positive. Furthermore, the children's language abilities at age three years were good predictors of later language abilities at nine years (Walker, Greenwood, Hart, & Carta, 1994). Various methods of language instruction have been developed over the years to assist children who present with language delays. Some of these methods are characterized as trainer-directed (e.g., discrete trial instruction) and others are considered more naturalistic (Fey, 1986). The latter include incidental teaching (e.g., Hart & Risley, 1975), mand-modeling (e.g., Rogers-Warren & Warren, 1980; Warren, McQuarter, & Rogers-Warren, 1984), and delayed prompt or time-delay (e.g., Halle, Marshall, & Spradlin, 1979). These more naturalistic procedures have been combined into a comprehensive teaching strategy called milieu language teaching (e.g., Kaiser, 1993). Taken as a whole, these procedures will be referred to as naturalistic language teaching (NLT) for the purposes of this paper. …