A Solution to the Measurement Problem in the Idiographic Approach Using Computer Adaptive Practicing

Molenaar’s manifesto on psychology as idiographic science [1] brought the N = 1 times 1 series perspective firmly to the attention of developmental scientists. The rich intraindividual 2 variation in complex developmental processes requires the study of these processes at the level of the 3 individual. Yet, the idiographic approach is all but easy in practical research. One major limitation is 4 the collection of short interval times series of high quality data on developmental processes. In this 5 paper we present a novel measurement approach to this problem. We developed an online practice 6 and monitoring system which is now used by thousands of Dutch primary school children on a daily 7 or weekly basis, providing a new window on cognitive development. We will introduce the origin of 8 this new instrument, called Math Garden, explain its setup, and present and discuss ways to analyze 9 children’s individual developmental pathways. 10