The purpose of the present study was to evaluate the psychometric properties of Raven's colored progressive matrices by estimating the presence of pseudo-guessing and pseudo-carelessness. Participants were 1127 children from ages 5 to 11. Guessing and carelessness were assessed using the lower and upper asymptotes of the 3PL and 4PL item response theory (IRT) models, respectively. Optimal model fit was judged using difference loglikelihood tests and information criteria. Results indicated that guessing, but not carelessness, were evident in the AB and B forms of the CPM, with successful guessing being more prevalent in the AB form. It is concluded that nonverbal IQ estimation in CPM should include variable estimation methods so that aptitude scores are estimated with the highest possible accuracy.