How Important Is Parental Time? It Depends: Comment on Milkie, Nomaguchi, and Denny (2015)

I enjoyed reading Milkie, Nomaguchi, and Denny's (2015) article and appreciate being invited to comment on it. Let me say at the outset that I think the authors tackled an important question and did so in a careful manner. To recap theirmainresults,holdingotherfactorsconstant, they find that the amount of time mothers spend with their children or adolescents has few significant associations with child or adolescent outcomes (even when they focus on a measure of "engaged time," which captures the time mothers were actually engaged with their children rather than simply present).Specifically, the authors find no significant associations between amount of time mothers spendandmothers'reportsofbehaviorproblems for children age 3-11 or reading or math scores for children age 6-11 or two measures of adolescents' risky behaviors. But there are also some important exceptions. The amount of time mothers spend with their children is associated with less delinquency reported by their adolescents. In addition, the amount of time mothers and fathers spend together with their children is associated with several adolescent outcomes: fewer externalizing problems, higher math scores, less substance use, and less delinquent behavior. So, at the end of the day, we are left with a somewhat mixed picture. Amount of time seems not to matter for school-age children, but it does for adolescents, but results vary depending on whether mother or parent time is considered and depending on which specific outcome is examined.I'll begin with some caveats and limitations related to these results. Several (although not all) of these were pointed out by the authors themselves, but I tend to place somewhat more weight on some of them than they do. But I'll devote most of this commentary to some issues that were not addressed in the article.Caveats and LimitationsMilkie et al. are careful to note that there are several important caveats and limitations related to their results. For example, they discuss the fact that they are not able to assess the quality of time that mothers (or parents) are spending with their children. I agree with the authors that this is an important point, but I don't have much to say about it beyond what they have said already.The authors also mention the possibility that mothers who spend more time with their children might be a select group and that this might bias their results. But they suggest that this concern is somewhat muted in the present case given that they mainly find null results. Although they provide some discussion on this point, I think it deserves more attention. My concern is the following: If it is beneficial for children to have mothers (or parents) spend more time with them, but the mothers (or parents) who select into more time are negatively selected (or if their children or adolescents are negatively selected), then the null findings would in fact be biased, because a potentially positive effect of mother (or parent) time would be offset by the correlation of more time with unobserved factors that are associated with poorer outcomes. So the fact that there are mainly null findings does not mean we need not be concerned about selection bias.Another potential source of bias, which Milkie et al. don't flag as such, is the fact that the measures of child behavior are parent reported. Although this is often the case in developmental research, it does not mean it is not a problem. Perhaps mothers who spend more time with their children are more aware of their behavior problems, or perhaps those who believe their children have more behavior problems report spending more time with them. Again, this could lead to bias-with more time with children being correlated with more behavior problems not because the two are causally linked but because mothers tend to report the two things together. For this reason, I would place more weight on the results from measures that are not reported by mothers-the children's reading and math scores and the adolescents' self-reported risky behaviors. …