People have long been tempted to link brain size and cognition. The intuitive notion that a “big brain” means “more intelligent” was first threatened some time ago, when we discovered animals with larger brains than ours: elephants and whales. Sure as we were of humankind’s superior intelligence, we still felt the need to prevail, so we gamely parried: Perhaps it is the brain size relative to body size that makes our brains the biggest. Though humans come out well there, too, this measure is biased toward birds and other small animals that have relatively large brains for their bodies. After more deliberation, scientists finally offered up the so-called “encephalization quotient”: brain size relative to the expected brain size in related taxa. On top: humans. Phew.
Consider, though, the strange case of that growing child.
Every infant’s brain develops through a period of synaptogenesis – wanton proliferation of synapses, which are the connections between neurons – in the first year or so of life. But one could argue that it is when this intense brain growth ends that the real growth of the child qua individual begins. The next phase of brain development occurs in large part through an increase in synaptic pruning: paring of those connections that are not useful for perceiving, considering or understanding the world the child is facing. In this sense, it’s by downsizing that an individual’s brain is born.
The Dish 