Does quality of child care affect child outcomes at age 41/2?

Research reveals associations between child-care quality and child outcomes. But are these associations causal? Data from the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care, a longitudinal study of children from birth to age 4(1)/(2), were used to explore 5 propositions that would support a causal argument. Three propositions received support, principally in the cognitive domain: (a) Associations between quality and outcomes remained even with child and family factors controlled; (b) associations between care and outcomes were domain specific; and (c) outcomes were predicted by quality of earlier care with concurrent care controlled. The 4th proposition, that associations between quality and outcomes would be significant with earlier abilities controlled, received limited support. There was no support for the 5th proposition, that quality and outcomes would exhibit dose-response relations.