Misconception: The IQ is a direct measure of brain performance. For example, somebody with an IQ of 120 can do 20% more mental work in the same amount of time than somebody with an IQ of 100.
In truth the IQ is a purely statistical measure. It has no direct relation to brain performance, is not proportional to it, and doesn't even have any linear or otherwise straightforward relation to it. The only thing you can say is that somebody with a higher IQ will show higher scores on most other brain performance tests as well, but the IQ doesn't say how much higher.
http://www.michna.com/iq.htm
Relevant paragraph quoted:
Misconception: The IQ is a direct measure of brain performance. For example, somebody with an IQ of 120 can do 20% more mental work in the same amount of time than somebody with an IQ of 100.
In truth the IQ is a purely statistical measure. It has no direct relation to brain performance, is not proportional to it, and doesn't even have any linear or otherwise straightforward relation to it. The only thing you can say is that somebody with a higher IQ will show higher scores on most other brain performance tests as well, but the IQ doesn't say how much higher.