Five-year-old Mary watches while her teacher pours equal amounts of water into two similar glasses. The liquid from one of the glasses is then poured into a tall, thin container, and Mary is asked which contains more—the original glass or the tall, thin container. She says the tall, thin container contains more liquid. According to Jean Piaget, this example illustrates a lack of

The answer is concept of conservation.

Explanation:

Understanding the concept of conservation involves realising the distribution or shape of an object does not change the properties of the object itself. For example, a child who understands that a chocolate bar sliced into six pieces is still the same amount of chocolate, has likely acquired the concept of conservation.

According to Piaget, this ability appears during the concrete operational stage (around ages 7 and 11).  

well this isn't a question but if you are asking if it is true or false it is, true.