Sarah Kendig and Suzanne Bianchi from University of Maryland examined differences in the amount and type of time that single, cohabiting, and married mothers spend with their children.
They found that cohabiting and married mothers spend similar amounts of time caring for their children, while single mothers spend less time with their children than married mothers.
However, if single mothers had the same level of education and employment as married mothers, they would spend the same amount of time with their children.
The reason why single mothers spend less time is they have higher employment rates - and employed mothers spend less time caring for their children than mothers who are not employed.
"This suggests that if we want to equalize maternal investments in time with children, we could do so by encouraging policies that focus on improving educational and employment opportunities for single mothers," the authors conclude.
This study is published in the November 2008 issue of the Journal of Marriage and Family.