“…The models had three levels: infant, test session, and stimulus sort. Based on the results of earlier analyses (see, e.g., Butcher et al, 2000;Hunnius & Geuze, 2004a), the development was described using three piecewise linear age functions (age periods 6-9, 9-16 and 16-26 weeks). The data were centered around 12 weeks of age, as this was approximately the middle of the period in which the largest changes were expected.…”