There are two parts to the diagram: An upper section showing each stage as a stack of blocks - stage one has one block, stage two has two blocks, stage three has three blocks, and stage four has four blocks. The lower section is made up of text explaining how a child’s stage of cognitive development is assessed. Stage one is the Sensorimotor stage, which occurs from birth to two years. Attached text explains that in sensorimotor stage, the child uses sensory capabilities and motor activities to learn about the world, and develops object permanence. Stage one is assessed by using the object permanence test, which text explains as follows: “does the child realize objects continue to exist when they are hidden? Infants who have developed object permanence will search for an object.” Above this text is a photograph of a baby sitting at a table, with a divider on it. On the other side of the divider, hidden from view, is a teddy bear. Stage two is the pre-operational stage, which occurs from two to 7 years of age. Attached text explains that in the pre-operational stage, the child uses symbolic thinking to explore and understand the world. Children at this stage are known for magical thinking and egocentrism.” Text in the lower section explains that the “Three mountains task tests egocentrism. Can the child imagine a perspective different than her own? ‘What would you see if you were standing at Point B?’” Above this text is a three-dimensional illustration of three mountains on a rectangular plane. The four sides of the plane are labeled A, B, C, and D, respectively. Stage three is the concrete operational stage, which occurs from 7 to 11 years. Attached text reads “Child understands operations and thinks more logically in reference to concrete objects and circumstances”. Text in the lower section explains that the “Conservation of volume test assesses understanding of operations. Does a child understand that the amount of liquid remains constant when it is pared into a container with a different shape?” Above this text is an image of a girl looking at two differently shaped containers, each with liquid in them. Stage four is the formal operational stage, which occurs from 11 years of age and up. Attached text reads “Child is now able to think logically and systematically and is capable of hypothetical thinking.” Text in the lower section explains that the “Third eye task tests formal operational thought. ‘If you had a third eye, where would you put it?’ Children at this stage come up with logical, innovative answers.