While a large literature has focused on the impact of parental investments on child cognitive development, very little is known about the children's own investments. Information on how children use their time separately from parents is probably less informative for babies and toddlers, but it becomes more important in later stages of life, such as adolescence, when children start to take decisions independently. The objective of this research is to explore and compare the impacts of time investments by parents and children on child cognitive outcomes. By using the Child Development Supplement of the PSID (Panel Study of Income Dynamics) 1997-2007 we show that own time investments have a significant effect on cognitive outcomes of children aged 11-15, while mothers' time inputs appear less important. For younger children, the impact of mothers' time is greater.