Apparently, children are impatient and probably not rational according to Eric Bettinger and Robert Slonim in an article published in the Journal of Public Economics (Feb 2007). The abstract is below. The most interesting thing is the lack of a relationship between mathematical ability and discounting.
Recent policy initiatives offer cash payments to children (and often their families) to induce better health and educational choices. These policies implicitly assume that children are especially impatient (i.e., have high discount rates); however, little is known about the nature of children's patience, how it varies across children, and whether children can even make rational inter-temporal choices. This paper examines the inter-temporal choices of 5- to 16-year-old children in an artefactual field experiment. We examine their choices between varying levels of compensation received in 2 or 4 months in the future and in 0 or 2 months in the future. We find that children's choices are consistent with hyperbolic discounting, boys are less patient than girls, older children are more patient and that mathematical achievement test scores, private schooling and parent's patience are not correlated with children's patience. We also find that although more than 25% of children do not make rational inter-temporal choices within a single two-period time frame, we cannot find variables that explain this behavior other than age and standardized mathematical achievement test scores.
