This theory of cognitive development is known as the "Stages Theory", a comprehensive set of observations made by Piaget detailing four stages in which cognitive development occurs. human intelligence (Huitt et al 2003 ). Firmly rooted in evolution and biology, Piaget's stage theory articulates key differences in the growth of individuals during the first years of life. He believed that everyone goes through the four stages in exactly the same order. The phases are as follows: the sensorimotor phase, the pre-operational phase, the concrete operational phase and the formal operations phase (Woolfolk