90 5-11 yr olds were tested on 2 variations of Piaget's spatial perspective task. The predominance of each of 4 kinds of spatial errors (interposition, aspect, distance, and right-left) was found to be differentially related both to age and overall task performance. The significance of this developmental sequence and the method of error analysis employed are discussed in the context of the earlier work of Piaget and B. Inhelder. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1973 American Psychological Association.