Chimerism is what happens when cells from one twin are present in the other. For example, white blood cells with Y chromosomes would be found in the female twin. Vigier et. al, 1989.
Piaget's theory of cognitive development. Piaget's theory of cognitive development is a comprehensive theory about the nature and development of human intelligence. It was first created by the Swiss developmental psychologist Jean Piaget (1896â1980).
People accumulate all this useful knowledge through the process of cognitive development, which involves a multitude of factors, both inherent and learned. 1  Cognitive development in childhood is about change. From birth to adolescence a young person's mind changes dramatically in many important ways.