Bigger is better, right? If you’re trying to insult someone you might call them a “pea brain” or tell them they have a “bird brain,” but as it turns out, brain size does not correlate with intelligence. The human brain, in relation our body size and that of other primates, is bigger than the brains of apes or monkeys, and it’s been steadily gaining in size over the past couple of million years. However, once humans evolved enough to know how to use stone tools, about 20,000 years ago, that growth stopped and declined by about 10%, which equals an amount of tissue about the size of a baseball. Humans are continuing to gain skills and intelligence, however, so the connection between size and knowledge isn’t there.
Research doesn’t bear it out either. In a 2015 meta-analysis (essentially a study of all the studies) when differences in brain size were compared with differences in intelligence, there was almost no connection between bigger brains and smarter people. Many studies point not to size, but to connectedness. How the brain regions communicate with each other, and how neurons parse signals across the brain is what matters and, as it happens, less is more. It’s not about how many connections there are, but rather the efficiency of a leaner more well connected set of nerve cells…quality over quantity. Neurons send signals over dendrites, small spines that protrude from the cells. The fewer dendrites there are, the more efficient the network.