The Size of the Human Brain

The human brain is an amazing organ. It's capable of surprising feats of memory and learning. It's susceptible to damage, and yet remarkably adaptable to change. Considering all it can do, you might wonder how big the brain is.

While the human brain has a structure similar to that of other mammals, what makes it different is the brain's size in relation to the rest of the body.

Human Brain Size Stats

The average adult human brain weighs about 3 pounds (1300 to 1400 grams). A newborn human baby's brain weighs approximately 350 to 400 grams or three-quarters of a pound. The average brain is around 15 centimeters long.

Men tend to have bigger brains than women. After taking overall body weight into account, men's brains tend to be approximately 100 grams larger than women's.

In women, parts of the frontal lobe and limbic cortex (areas associated with problem-solving and emotional regulation) tend to be bigger than those of men. In men, the parietal cortex (associated with the perception of space) and amygdala (involved in the processing of memory and emotional responses) tend to be larger than those in women.

Neurons are the building blocks of the brain and nervous system. They transmit and carry information, allowing different parts of the brain to communicate. They also allow the brain to communicate with other parts of the body. Researchers currently estimate that there are around 86 billion neurons in the human brain.

Does Brain Size Matter?

Humans do not all have the same size brain. Does that mean that highly intelligent people have bigger brains? In some cases, there might be a link.

Autistic children tend to have bigger brains (and earlier disproportionate brain growth) than non-autistic children. The hippocampus (an area of the brain strongly associated with memory) tends to be smaller in older adults with Alzheimer's disease.

What about intelligence? It depends on who you ask. According to one analysis by Michael McDaniel of Virginia Commonwealth University, many studies have found a correlation between bigger brains and higher intelligence.

However, not all researchers agree with McDaniel's conclusions. Such studies also raise important questions about how we define and measure intelligence, whether we should account for relative body size when making such correlations, and which parts of the brain we should look at when making determinations about intelligence.

It is also important to note that when looking at individual differences, brain size variations between people are relatively small. Other influences that could play a pivotal role include the density of neurons in the brain, social and cultural factors, and other structural differences inside the brain.