One of the major accomplishments of concrete operational stage is

According to Piaget's theory of cognitive development, the concrete operational stage (ages 7-11) is marked by the development of logical thinking about concrete objects. A major accomplishment of this stage is conservation - the understanding that quantity remains the same despite changes in shape or arrangement. Animistic thinking belongs to the preoperational stage, hypothetico-deductive reasoning to the formal operational stage, and secondary circular reactions to the sensorimotor stage.