The development of the concept of seriation was studied for 415 children, ranging in age from 3 to 9 years. The subjects were required to learn to identify the larger or smaller object in a two stimulus series, the smallest or middle-sized object in a three stimulus series, and the largest or next to the smallest in a four stimulus series. The end…

Pattern of results is discussed in terms of the conceptualization that imitation required both that the observer (1) has acquired and retained the model's responses and (2) has been placed in circumstances which favor activating this learning into overt performance. (Authors)