This paper presents causal evidence on the impact of parenting practices on early child development. We exploit exogenous changes in nurturing care induced by a parent training intervention to estimate the impact of nurturing parenting practices on child outcomes. We find a large and significant impact measured at age two; in contrast, at age four nurturing care has only a modest, and imprecisely estimated, impact on child outcomes. This is despite the fact that the intervention induced substantial changes in parenting practices at both ages. The differential relationship between child development and nurturing care at ages two and four explains the fade-out in treatment effects for the intervention as a whole: although parents continued to respond, their response no longer had the intended effect on child outcomes. [Additional funding from the Royal Society of Edinburgh.]