One key idea of this thinker was adaptation, which occurred by taking mater
One key idea of this thinker was adaptation, which occurred by taking material in from the environment and noting their differences through assimilation and accommodation. In one experiment, this psychologist established the notion of "conservation of number" by rearranging the same number of objects, demonstrating that children lack it  until the age of 7. He proposed that children from the age of 2-7 learn to use language to represent objects, but classify them only by a single characteristic and are egocentric. That group was classified as "preoperational", which followed this man's "sensorimotor" stage. For 10 points each, identify this Swiss psychologist who developed four stages of cognitive development.
One key idea of this thinker was adaptation, which occurred by taking material in from the environment and noting their differences through assimilation and accommodation.
Jean William Fritz {Piaget}