The ages of birth to ten are a peak period of sensitivity for learning. During much of this time, a child's brain actually consumes twice as much glucose as an adult's. The infant brain doubles in size during the first year of life. At birth, each neuron in the cerebral cortex has around 2,500 synapses. By the age of two to three years, each neuron has 15,000 synapses. This massive growth in connectivity is matched by terrific pruning. As the brain adapts itself to its surroundings and becomes more specialized, old connections are pruned away. This is the main mechanism by which cognitive development fits itself to the social and cultural environment of the child. Yet although the plasticity of the developing child's brain is remarkable, equally remarkable is the similarity in cognitive development that is found across cultures and social contexts.