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).
Theories of Cognitive Development. Cognitive development refers to the change in childrenâs patterns of thinking as they grow older. Jean Piagetâs Stage Theory. The scientist best known for research on cognitive development is Jean Piaget (see pages 72â75), who proposed that childrenâs thinking goes through a set series of four major stages.