Data from the NICHD Study of Early Child Care and Youth Development were used in this investigation, because they include repeated measures of child care experiences, externalizing behavior, and family characteristics. There were three main findings. First, the evidence linking child care hours with externalizing behavior was equivocal in that results varied across model specifications. Second, the association between child care hours and externalizing behavior was not due to a child effect. Third, child care quality and proportion of time spent with a large group of peers moderated the effects of child care hours on externalizing behavior. Child care hours was more strongly related to externalizing behavior when children were in low-quality child careand when children spent a greater proportion of time with a large group of peers. The magnitude of associations between child care hours and externalizing behavior was modest. Implications for parents and policymakers must take into account that externalizing behavior is predicted from a constellation of variables in multiple contexts.
TIME IN CHILD CARE Testing a Series of Causal Propositions Relating Time in Child Care to Children's Externalizing BehaviorReviewers of the literature on early child care have frequently noted an association between spending more time in child care and exhibiting more externalizing behavior, such as assertive, disobedient, and aggressive acts (Belsky, 1986;2001;Clarke-Stewart & Fein, 1983).Longitudinal investigations of externalizing problems indicate that these behaviors often persist into elementary school (Campbell, 1995(Campbell, , 2002Campbell, Pierce, Moore, Marakovitz, & Newby, 1996;Verhulst & Van der Ende, 1992) and that elevated levels of externalizing problems are accompanied by peer rejection and poor academic performance (Campbell, 2002;Farmer & Bierman, 2002). Behavior problems can interfere with a child's acquisition of age-appropriate skills (Campbell, 2002), potentially leading to antisocial behavior in adolescence (Zahn-Waxler, Usher, Suomi, & Cole, 2005) and adulthood (Levenston, 2002). Even though child care experience has not been linked to clinical levels of problems, researchers and policymakers have worried that extensive use of child care in the early years might be a risk factor for increasing problem behaviors without causing clinical problems.Studies have demonstrated that children exhibit more of these negative behaviors if they spend more time in care before they enter kindergarten (Bates, Marvinney, Kelly, Dodge, Bennett, & Pettit, 1994;Magnuson, Meyers, Ruhm, & Waldfogel, 2004;Vandell & Corasaniti, 1990), are in more hours of care in the first year of life (Hofferth, 1999), start care at younger ages, or spend more hours there each day (Loeb, Bridges, Bassok, Fuller, & Rumberger, 2007).In the NICHD Study of Early Child Care and Youth Development (SECCYD), associations were documented between the amount of time children had spent in child care and externalizing behavior at 24 months of age (NICHD Early C...