Many claim there is not one kind of intelligence, but at least eight different types, including verbal, spatial and emotional intelligence
Argument rages as to whether intelligence is biologically or socially determined
The brain weighs less than 2.5% of our total bodyweight, but accounts 20% of our energy consumption when we're at rest. It burns oxygen and glucose at ten times the rate of other body organs
Each year 10,000 people take the MENSA IQ test - 2,500 pass to become members. Over the last century, the UK's average IQ has risen about 3 points every decade
IQ depends on your culture, class and gender because of the way tests are written. Controversially, in the 1920s IQ tests were used to assess the suitability of immigrants for US citizenship
What is intelligence?
Defining intelligence is highly problematic. Is there an 'intelligence' that equips us to solve all kinds of problems and answer all questions, regardless of their nature? Or are there different intelligences that help us deal with particular problems and solutions? The scientific community is divided on the issue.
One of the main tenet's underpinning the idea of a single entity 'intelligence' is the concept of 'General Intelligence', or 'g'. Devised by English Psychologist, Charles Spearman, in the early 20th Century 'g' was a statistical measure of performance across a variety of tests.
Spearman found that the same people who did well in a variety of mental tests tended to use a part in their brains that he termed 'g'. This 'g' laid the foundation for the notion of a single intelligence, which enables us to undertake everyday mental tasks.
A recent study seems to endorse Spearman's theory. Research has found that a part of the brain called the 'lateral prefrontal cortex' is the only area of the brain to increase in blood flow when volunteers tackle complicated puzzles.
Spearman's concept, however, is still highly controversial with many people questioning both the statistical process and the simplistic nature of 'g'. There is also a body of research that states that our mental ability is a function of social factors such as education and not one's inherent biological make-up.
Intelligence and the brain
The early Greeks thought the brain was the home of your soul, rather than your intellect. They believed that thinking happened somewhere around the lungs! Not until the seventeenth and eighteenth centuries was the brain seen as an organ of intelligence and thought, when the concept of the mind emerged.
Using new forms of technology, scientists have been able to look at how the brain performs when we undertake different tasks. Roll the pointer over the brain below to find out how our brain processes language.
