Bigger brains mean higher IQ

People with bigger brains tend to score higher on standardized tests of intelligence, new research shows.

However, study author Dr. Michael A. McDaniel of the Virginia Commonwealth University in Richmond emphasized that these findings represent a general trend, and people with small heads should not automatically believe they are less intelligent.

For instance, Albert Einstein's brain was "not particularly large," McDaniel noted.

"There's some relationship (between brain size and intelligence) on average, but there's plenty of room for exceptions," he told.

Interest in the relationship between brain size and intelligence grew in the 1830s, when German anatomist Frederick Tiedmann wrote that he believed there was "an indisputable connection between the size of the brain and the mental energy displayed by the individual man."

Since that statement, scientists have conducted numerous studies to determine if Tiedmann's assertion was, in fact, correct. Most studies have investigated the link between head size and intelligence. More recently, however, researchers have published additional studies on intelligence and brain size, measured using MRI scans.

For his study, McDaniel analyzed more than 20 studies that investigated the relationship between brain size and intelligence in a total of 1530 people.

The studies showed that on average, people with larger brain volumes tended to be more intelligent. The relationship between brain size was stronger in women than men, and in adults than children, McDaniel notes in the journal Intelligence.

In an interview, McDaniel noted that he's not sure why the relationship was stronger for adults and women. Previous research has shown that women, on average, tend to have smaller brains than men, but score just as well - if not higher - in tests of intelligence, he said.

McDaniel insisted that the relationship between brain size and intelligence is not a "perfect" one. "One can certainly find lots of examples of smaller-brained people who are highly intelligent," he said. "But, on average, the relationship holds."

SOURCE: Intelligence, online June 16, 2005.