Research studies by psychologist demonstrated that infants acquire object permanence at a much younger age than piaget believed.

The answer is Renée Baillargeon. She is an Alumni Well-known Professor of Psychology at the University of Illinois Urbana-Champaign. She specializes in the development of perception in infancy. She contends that Piaget's discovery concerning infants' failure to understand object permanence until 8–12 months old was engrained in a deficiency of motor ability as contrasting to inadequate cognitive development.

answer; when one group has an extremely high score at pretest;