 Piaget's theories of infant development were based on his observations of his own three children.While this clearly presents problems with the sample size, Piaget also probably introduced confounding variables and social desirability into his observations and his conclusions based on his observations.It is entirely possible Piaget conditioned his children to respond in a desirable manner, so, rather than having an understanding of object permanence, his children might have learned to behave in a manner that indicated they understood object permanence.