In 1919, Piaget conducted intelligence tests under the direction of Alfred Binet. Piaget became fascinated not so much with measuring IQ as with determining why children made logical errors. Piaget subsequently devoted his life's work to determining how children passed through stages of cognitive development–via assimilation and accommodation –to construct cognitive schemas.
Piaget conducted empirical research on "genetic epistemology" – the sequential development of logic throughout childhood. He concluded that, "the growth of knowledge is a progressive construction of logically embedded structures superseding one another by a process of inclusion of lower less powerful logical means into higher and more powerful ones up to adulthood."
Piaget used the term assimilation to refer to the process in which an individual adjusts mentally to the environment. This process might require a reinterpretation of the evidence of their senses. Accommodation involves the internal modification of mental concepts that accompanies assimilation.
Piaget's research followed children's cognitive development from birth through to the stage of formal operations (~ age 11). Children pass through substages and stages in a set sequence, building each cognitive schema upon that preceding. However, beyond the logical schema acquired in childhood, not all individuals attain the full repetoir of logical operations necessary for critical thinking. The worldviews of many adults exhibit considerable philosophical tension, and many adults display internally inconsistent, illogical, emotional reasoning fraught with many of the errors found in fallacious arguments. Religious beliefs, particularly those of YECs and other creationists, force illogical inconsistencies into the thinking process.