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).
Cognitive development is Jean Piaget's theory. Through a series of stages, Piaget proposed four stages of cognitive development: the sensorimotor, preoperational, concrete operational and formal operational period. The sensorimotor stage is the first of the four stages in cognitive development which extends from birth to the acquisition of language.