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).
Piaget's cognitive theory states that, children's language reflects the development of their logical thinking and reasoning skills in stages, with each period having a specific name and age reference. There are four stages of Piaget's cognitive development theory, each involving a different aspect of language acquisition: 1  Sensory-Motor Period- (birth to 2 years) Children are born with action schemas to assimilate information about the world such as sucking or grasping.