Answer:
Zone of proximal development
Step-by-step explanation:
Zone of proximal development is a stage in a child's development, where the child is provided support to perform a task. It is a level in a child's development which is between the actual development and potential development. This joint learning activity is usually between the child and an older person, who acts as an educator.
Stephen had unsuccessful attempts in assembling the moderately sized jigsaw puzzles on his own and with the help of his older brother he assembled it. Here Stephen engages in joint activity with the brother to solve the puzzle and he falls in the zone of proximal development