True or false: Walter is taller than Scott, and Scott's little brother is taller than Roger. Since Walter is not the tallest one of the four, then Scott's little brother must be tallest. Confusing? It's meant to be. This is the sort of question you might encounter on an IQ test.

IQ tests measure a specific kind of intelligence called cognitive ability, meaning the ability to solve problems and grasp concepts. A typical test measures things such as reasoning skills, problem-solving capacity, and memory. The score you receive rates your cognitive ability compared to the general population. A score between 90 and 110 indicates average intelligence, while a score above 130 indicates exceptional intelligence. A score below 70 may indicate mental retardation.

You might object, isn't intelligence a matter of one's environment? To the contrary, say many psychologists who believe that there is a general factor of intelligence that has more to do with biology than with environment. Although culture plays a role in modifying intelligence, according to these psychologists people are born with varying levels of cognitive ability. In short, some people are smarter than others.

If this strikes you as unfair, fear not. Many scientists reject the notion of generalized intelligence, arguing instead that people have only collections of abilities to perform various specific tasks. Furthermore, intelligence may be measured in various ways, including creativity, imagination, and empathy. So if you're better at telling stories than solving story problems, take heart. You're not dumb, just intelligent in a way not measured by IQ.