The question of whether brain size affects intelligence is heavily debated in science, and there is no certainty on the issue. There is evidence to suggest that brain size can make a difference, but there is also evidence suggesting that it isn’t the most important factor. According to some experts, brain size seems to be more important to some kinds of intelligence than others. There are studies in the animal kingdom that have also shown large contradictions regarding brain size and intelligence among different species, and this has generally made scientists more uncertain about the issue.
Animals that have made scientists most uncertain are birds. Many bird species, especially those in the crow family, show very complicated social behaviors and demonstrate the ability for complex reasoning. They are generally able to do this despite the fact that their brains are smaller than many species with less formidable cognitive abilities. Some experts think this is because birds have particularly complex neuron structures that allow their brains to be more efficient.
There are also other studies that show a strong direct relation between brain size and intelligence. These studies have examined intelligence tests across a wide array of species and have focused on a more general type of problem-solving ability. The reason for these results is disputed. Some experts think that simply being larger physically causes the animals to require more intelligence for some reason, while others think that brain size is the primary factor.
In people, studies of brain size and intelligence have also been relatively contradictory. For example, most men have larger brains than most women, but studies have been unable to find statistically significant differences in intelligence between men and women. There are many cases where people with much smaller brains have been able to demonstrate much more mental capacity than people with larger brains. It is generally true that brain size and body size are usually proportionally-related among humans, but intelligence and body size are often totally unrelated.
Some experts think that the structure of the brain, or maybe the specific size of certain parts of the brain, have more to do with intelligence. There is also evidence that brain size changes based on a person’s experience, and as people gain more mental knowledge, their brains may actually grow. There is a lot of evidence to suggest this happens during the childhood years when people are developing, but there is also some evidence showing that it happens after people reach adulthood as well.