MULTIPLE-SPELL, DISCRETE-TIME SURVIVAL ANALYSIS OF DEVELOPMENTAL-DATA- OBJECT CONCEPT IN PIGTAILED MACAQUES

To measure cognitive development in 123 pigtailed macaques, we calcula ted medians and quartiles for the milestones of classical (Piagetian) object concept development (plain reach, partial-hide, full-hide, and A-not-B) in both 2-dimensional (screen) and 3-dimensional (well) tasks . Using multiple-spell, discrete-time survival analysis, we examined t he influence of 4 independent variables (starting age, sex, birth weig ht and task) on the probability of completing the milestones on any gi ven test The significant predictors for completion of the well sequenc e were birth weight and task. The best predictors for completion of th e screen sequence were birth weight, number of test sessions, and inte raction between birth weight and task. Birth weight had a greater pred ictive relationship in the earlier stages. This analysis provided info rmation that cannot be obtained with traditional parametric methods.