Resolving the Contradictory Conclusions from Three Reviews of Controlled Longitudinal Studies of Physical Punishment: A Meta-Analysis

Three literature reviews of controlled longitudinal studies of child outcomes of customary physical punishment have arrived at contradictory conclusions. We attempt to explain the contradiction using meta-analyses based on two types of change-scores and two sensitivity tests. We hypothesized that studies employing standard ANCOVA-type longitudinal analyses would suggest harmful-looking (but trivial) effects, and studies employing simple difference scores would suggest beneficial-looking (but trivial) effects of customary spanking on four child outcomes. We hypothesized that age (18 mos − 11 yrs) would moderate these associations. We hypothesized that spanking to enforce timeout in randomized studies of clinically defiant young children would predict large improvements in children’s cooperation with timeout and parental commands. All hypotheses were supported. Regardless of statistical method, customary spanking explained less than 1% of the remaining variance in each child outcome (after controlling for baseline adjustment). The oft-reported harmful-looking outcomes of customary physical punishment in ANCOVA-type analyses are likely due to residual confounding. Various methodological problems and needed innovations in parental discipline research are discussed. Given the seeming near-zero effect of customary spanking, and the large beneficial-looking effects of spanking to enforce time-out in clinic-based intervention programs, blanket anti-spanking injunctions are discouraged.