Increased agricultural production and the growth of craft products contributed to the formation of different social groups in ancient Sumer, as people began to earn more material goods and increased their wealth with the arrival of agriculture in Mesopotamia. Some citizens became very wealthy as a result of this constant income, while others remained peasants. People began to own portions of land that had previously been farmed by peasants as modern agriculture techniques developed. Artisans and traders who sold goods established a healthy way of life as well. In ancient Sumer, these various labor activities formed social groups, which later enabled Sumerians to create powerful city-states.
Lee Vygotsky in his social development theory aserts that social contact and activity is important for a child's intellectual development and that both biological development and cultural experience influence children's ability to learn and think.
