When animals reared from birth in physically and socially stimulating surroundings are compared with those reared in isolation, the brains of the stimulated animals

The brain and synapses are denser

Explanation: Researchers aimed to discover the relationship between social factors in our environment and brain development in infants by studying animals in different environments. The result of these studies shows that the brain and synapses are denser in animals that are reared in socially stimulating environments than those raised in isolation from birth.

This is applicable to human children born prematurely and have to spend a considerable amount of time in intensive care units. They are under stimulated, and need extra stimuli to ensure development is at the same rate as babies who grow in a home where social interaction is present.