 The idea was to change the approach described in his book "The Child's Conception of the World" and move away from the vague questioning interviews.This new approach was described in his book "The Child's Conception of Physical Causality", where children were presented with dilemmas and had to think of possible solutions on their own.Later, after carefully analyzing previous methods, Piaget developed a combination of naturalistic observation with clinical interviewing in his book "Judgment and Reasoning in the Child", where a child's intellect was tested with questions and close monitoring.