seek to promote child development indirectly by enhancing the general quality of the caregiving environment (Farran, 2000). Similarly, services that are focused explicitly on parenting behaviors have greater impact on parent-child interactions than do generic parent education efforts (Brooks-Gunn et al., 2000). These patterns are reflected in the relatively greater child-focused impacts of center-based interventions (Farran, 2000) and greater parent-focused effects of home-based programs (Brooks-Gunn et al., 2000). A confirmatory review of 27 early intervention programs by Benasich and colleagues (1992) found short-term child cognitive benefits in 90 percent of center-based services, in contrast to 64 percent of home-based interventions. One year after program termination, child developmental gains persisted for 67 percent of the center-based programs and 44 percent of the home-based interventions.

Research demonstrating differential effectiveness for specific subgroups of children and families further supports the need for individualization of services to ensure maximum impact. For example, children whose mothers had the lowest IQ gained the most from the Abecedarian Project (Campbell and Ramey, 1994, 1995). Similarly, children whose mothers had less education demonstrated greater benefits from the Infant Health and Development Program, although greater child impacts were also documented for children at lower biological risk as measured by birthweight (Brooks-Gunn et al., 1994; Liaw and Brooks-Gunn, 1993; McCarton et al., 1997). For children with defined disabilities, both the nature of the impairment and its level of severity demand a highly differentiated approach to service planning and delivery. Generally speaking, for both biologically and environmentally vulnerable populations, program impacts are generally greater for more disadvantaged families and for children with less severe disabilities (although the latter may be a function of the developmental measures that are used). More definitive understanding of the causal relations between specific interventions and specific outcomes for specific target populations will require further randomized experimental studies.

Linked to the need for individualized intervention strategies, current practice (and, in fact, federal law for children with disabilities) mandates that service outcomes be tailored to the particular interests of each individual family (Meisels and Shonkoff, 2000). In this context, parents of children with the same developmental disability may have very different goals and aspirations. Similarly, families experiencing comparable levels of economic hardship may have different needs and desires for assistance.

Quality of Program Implementation

The extent to which model demonstration programs are endowed with abundant resources and highly trained staff, evaluated successfully, and



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