Metacognition—awareness, monitoring, and regulation of one's own cognitive processes—includes metacognitive knowledge (understanding what strategies work in different contexts) and metacognitive monitoring (evaluating one's own understanding in real-time). Young children have remarkably limited metacognitive awareness; school-age children develop explicit strategy use, error monitoring, comprehension checking, and self-correction. As metacognitive abilities improve, children become increasingly able to select appropriate learning strategies, allocate study effort effectively, and adapt approaches when initial attempts fail.
Engage children in think-aloud protocols while solving problems to observe and scaffold metacognitive monitoring. Review intervention studies showing how teaching explicit metacognitive strategies improves learning outcomes across domains.
Metacognition is often described as "thinking about thinking," but that phrase understates how practical and developmentally specific it is. From your study of Piaget's stages, you know that cognitive development moves from concrete operations (age 7–11) toward formal operations (11+), gradually enabling abstract, self-reflective reasoning. Metacognition is one expression of this transition: the ability to treat one's own mind as an object of thought, to ask "do I actually understand this?" rather than simply proceeding as if one does. Young children are remarkably bad at this — and that badness is not stupidity, it is developmental.
There are two distinct components. Metacognitive knowledge is declarative: what you know about how memory, attention, and learning work in general and in your own case. A child with good metacognitive knowledge knows that distributed practice is more effective than cramming, that re-reading is less effective than self-testing, and that they personally find visual diagrams more useful than verbal descriptions. Metacognitive monitoring is dynamic: the real-time tracking of your own comprehension as you read, listen, or problem-solve. It asks "Am I getting this?" and triggers a repair strategy — slow down, re-read, ask for help — when the answer is no.
Young children fail at metacognitive monitoring in a characteristic way: they overestimate their own comprehension and memory. In classic studies, children who have heard a story with deliberately inconsistent information report understanding it perfectly — they cannot detect the inconsistency because they are not actively monitoring. Similarly, children asked to study a list until they "know it" stop studying far too early; they have poor feeling-of-knowing calibration. Memory development gives them more capacity (from your prerequisite), but metacognition determines whether they use that capacity efficiently. A child who monitors poorly will re-read a passage they cannot summarize without noticing the gap.
The development of metacognitive skill accelerates during middle childhood (roughly ages 8–12) as children gain experience with formal schooling and explicit instruction. The school context itself is a metacognitive environment: tests force children to predict their own performance; feedback shows them when their predictions were wrong; demanding tasks expose the failure of passive reading. Explicit strategy instruction — teaching children to generate questions about what they read, to self-explain, to plan before solving problems — substantially improves metacognitive skill at ages where it would not develop spontaneously. This is why metacognitive training has some of the highest effect sizes in educational psychology: children who are explicitly taught to monitor and regulate their learning become dramatically more effective learners, because strategy use multiplies the value of their existing cognitive capacity.