Jonathan Guryan, Erik Hurst, and Melissa S. Kearney find that time spent taking care of children is positively correlated with education. They write,

We offer four possible explanations for why child care patterns by education differ from the leisure and home production patterns.

* Parents view the output of investing in children as being more of a luxury good than either traditional home production or leisure goods.
* Parents view market-purchased child care options as poor substitutes for parental time, relative to the degree of substitutability between expenditures and time in the production of typical home produced goods. Higher-educated parents may be more likely to feel that market alternatives are not good substitutes for their own time spent with their children.
* Higher-educated parents have a greater preference for the output generated by time spent with their children, at least relative to their preferences for home produced and leisure goods; or, conversely, lower-educated parents have a greater relative preference for their own leisure.
* The return to investment in children from higher-income/higher-education parents is higher. Importantly, this explanation requires that parents do not consider market alternatives to be highly effective substitutes for their own time spent in child care.

We cannot say which of these is responsible for the facts we found; more research is needed.

I would suggest that their next research project should concern time taking care of pets. If more-educated people spend more time taking care of pets, then I would lean to the luxury-good explanation and away from the investment-in-children explanation.

Thanks to Mark Thoma for the pointer.