Assessing motivation in children using a progressive ratio task.

The association of age and sex on the performance of a progressive ratio task was studied in 847 children, ages 4-14 years. Variations of this task have been used extensively with animals and to a lesser extent with humans to study factors that affect aspects of motivation. The participants in this study were required to press a response lever for nickel reinforcers during a 10 min period. One response was required to earn the first nickel and each subsequent nickel required an additional 10 more responses. Older children had a significantly higher breakpoint than younger children. This appeared to be mostly the result of older children having significantly shorter inter-response times than younger children. In addition, boys had significantly higher breakpoints than girls, especially at older ages. The results of this study illustrate that both age and sex influence the performance of this task and thus suggest that age and sex influence aspects of motivation in children. Further, characterization of performance of this task by humans facilitates comparisons with animal models and, thus, enhances its translational utility. Published by Elsevier B.V.