This study has investigated whether mental attentional capacity increases as a lineair function of age during normal childhood development, as was predicted from Pascual-Leone's neo-Piagetian theory. To test this prediction, Pascual-Leone's Figural Intersections Test (FIT) and Raven's Standard Progressive Matrices (RSPM) were administered to 215 children aged 5 to 12 years. The responses on the total set of items showed a good fit to the Verhelst and Glas generalization of the on-parameter logistic model. The estimated item parameters were used to construct to seperate mental attentional capacity scales. The average mental attentional capacity estimates of children aged 5 to 6, 7 to 8, and 9 to 10 were approximately localized in the predicted areas of the scale based on RSPM items. The average mental attentional capacity estimates based on the FIT items were localized above the predicted scale areas. Consequently, the results only partly provide empirical support for the assumptions of Pascual-Leone's theory.