11.3 Piaget’s Theory of Cognitive Development 191 I cover my eyes, can you still see me?). Complex concrete operations, such as putting items in height order, are easily achievable. Classification becomes more sophisticated, yet the mind still cannot master purely logical operations based on abstract logical representations of the observational world. e Formal: Abstract deductive reasoning, the process of forming, then testing hypotheses, and systematically reevaluating and refining solutions, develops at this stage, as does the ability to reason about purely abstract concepts without reference to concrete physical objects. This is adult human-level intelligence. Note that the capability for formal operations is intrinsic in the PLN component of CogPrime, but in-principle capability is not the same as pragmatic, grounded, controllable capability. Very early on, Vygotsky [Vyg86] disagreed with Piaget’s explanation of his stages as inherent and developed by the child’s own activities, and Piaget’s prescription of good parenting as not interfering with a child’s unfettered exploration of the world. Some modern theorists have critiqued Piaget’s stages as being insufficiently socially grounded, and these criticisms trace back to Vygotsky’s focus on the social foundations of intelligence, on the fact that children function in a world surrounded by adults who provide a cultural context, offering ongoing assistance, critique, and ultimately validation of the child’s developmental activities. Vygotsky also was an early critic of the idea that cognitive development is continuous, and continues beyond Piaget’s formal stage. Gagne [RBW92] also believes in continuity, and that learning of prerequisite skills made the learning of subsequent skills easier and faster without regard to Piagetan stage formalisms. Subsequent researchers have argued that Pi- aget has merely constructed ad hoc descriptions of the sequential development of behaviour [Gib78, Bro84, CP05]. We agree that