Source: Concepts and Theories of Human Development 2^nd edition by Richard M. Lerner, Random House, NY 1986

Piaget is neither the last nor the only word about human development – but the cognitive achievements and limitations he deals with summarize a great deal of experimental and practical experience.

All people, under some circumstances, conscious and unconscious, – have cognitive limitations that can be called “Egocentrism.” We are connected as we are – limited as we are – and habitual as we are. The more preoccupied an individual or group is, or the more automatic the responses involved are, or the more primal the emotional circumstances, the more primitive the thinking is likely to be.

All people have some difficulty distinguishing between the self and the external world – some difficulty differentiating between symbol and object, some difficulty distinguishing between thoughts about reality and the actual experience of reality, some notions of “imaginary audience” and “personal fable.”

These limitations are both understandable and unavoidable.

People should know about them.

They can lead to mistakes that can be understood, and avoided – if these limitations are taken into account when enough is going wrong to justify the effort.