The present study examined performance on a computerized version of the Wisconsin Card Sorting Test (WCST) in participants between 6 and 18 years. Test trials were presented upon request, without time constraints, and with a direct coupling between the participant's response and the onset of the feedback. The pattern of findings that emerged from the self-controlled computerized WCST permitted unique insights into the developmental changes in reasoning and attention regulation during childhood and adolescence. The number of WCST categories achieved developed linearly between 6 and 11 years and asymptoted beyond this age, whereas attentional responses continued to develop. More specifically, a decrease in distractive attention to correct feedback predicted performance in the younger group. In contrast, an increase in attention to error feedback predicted the number of WCST categories achieved by the older children. This pattern of findings indicates that, although trial-by-trial feedback monitoring is crucial for the successful detection of WCST categories in both younger and older children, the specifics of attention regulation differ greatly between children and adolescents.