A researcher shows a child two rows of coins. Then, the researcher compresses one row; no coins are added, no coins are taken away. After that, the researcher asks the child which row has more coins. Assume that the child is in Piaget's concrete-operational stage. How will he respond?

Both rows have equal amounts of coins.

Explanation:

Concrete-operational stage: In psychology, the concrete-operational stage the part of the cognitive-developmental theory which was proposed by Jean Piaget and is considered to be as the third stage in his theory. The concrete-operational stage starts around the age of seven and lasts through eleven years of age.

In the concrete-operational stage, a child develops logical thoughts. The stage is termed as concrete-operational because a child mentally operates on concrete events or objects. A child gains the ability of reversibility, transitivity, conservation, seriation, etc.

In the question above, the child will respond as both rows have an equal amount of coins being in a concrete-operational stage.