Any attempt to specifically teach the skills characteristic of a later stage of development would result in only superficial learning according to his assessment. Thus, discovery learning has been advocated in schools in line with Piaget's recommendations. Acceptance of Piaget's findings has not been uncontested, however. The tasks devised by Piaget have been criticised as unnecessarily difficult and irrelevant to the experiences of very young children. Research on the Theory of Mind has shown that even children as young as three or four years of age can appreciate that others may have a perspective that differs from their own.
Case isolates the role of memory capacity or executive processing space in cognitive development.
Therefore, Piagetian theory is linked with the two other theories of cognitive development representing explanatory frameworks within this field during the twentieth century. Reviewing recent developmental literature the influence of Piaget still appears to be strong. Some areas of his theory have been challenged and fallen out of favour in terms of on-going research. Others such as perspective-taking appear to be still undergoing investigation and opening useful lines of inquiry. It is difficult to imagine what developmental psychology would have been without the contribution of Piaget, or that the debt should ever go unacknowledged.