Based on the results of classical twin studies, it just doesn’t appear that parenting—whether mom and dad are permissive or not, read to their kid or not, or whatever else—impacts development as much as we might like to think. Regarding the cross-validation that I mentioned, studies examining identical twins separated at birth and reared apart have repeatedly revealed (in shocking ways) the same thing: these individuals are remarkably similar when in fact they should be utterly different (they have completely different environments, but the same genes).3 Alternatively, non-biologically related adopted children (who have no genetic commonalities) raised together are utterly dissimilar to each other—despite in many cases having decades of exposure to the same parents and home environments.3
One logical explanation for this is a lack of parenting influence for psychological development. Judith Rich Harris made this point forcefully in her book The Nurture Assumption (an absolute must read). 6 As Harris notes, parents are not to blame for their children’s neuroses (beyond the genes they contribute to the manufacturing of that child), nor can they take much credit for their successful psychological adjustment. To put a finer point on what Harris argued, children do not transport the effects of parenting (whatever they might be) outside the home. The socialization of children certainly matters (remember, neither personality nor temperament is 100 percent heritable), but it is not the parents who are the primary “socializers”, that honor goes to the child’s peer group (a fascinating topic, but one that merits its own separate discussion).