The debate over corporal punishment of children sits at an uncomfortable intersection of parenting research, cultural tradition, and genuine disagreement about what the evidence actually shows. The position of mainstream developmental psychology by 2011 was clear: spanking was associated with worse behavioral outcomes in children, damaged the parent-child relationship, and modeled the use of physical force as a conflict resolution strategy. The position of a significant portion of parents worldwide, including in the United States, was equally clear: they had been spanked, they were fine, and periodic physical discipline was part of responsible parenting.

The research literature had significant methodological challenges. Studies were observational rather than experimental — researchers couldn't randomly assign children to be spanked or not spanked — which made establishing causation rather than correlation difficult. Parents who spanked differed from parents who didn't on multiple dimensions beyond the spanking itself. Children who were spanked differed from children who weren't on behavioral dimensions that preceded the spanking.

Meta-analyses attempting to synthesize across dozens of studies found consistent associations between spanking and increased aggression, antisocial behavior, mental health problems, and damaged parent-child relationships. The associations held across studies, cultures, and methodologies.

Defenders of occasional spanking distinguished between abusive physical punishment and a controlled corrective smack, arguing that the research conflated the two. Critics of spanking argued that the distinction was difficult to maintain reliably under the emotional conditions in which physical discipline actually occurred.

The honest answer was that the research strongly suggested spanking was net harmful, while acknowledging that the evidence was observational and the effect sizes for occasional mild spanking were smaller than the evidence for severe corporal punishment.