The adult human brain usually weighs between 1 and 1.5 kg (three pounds) in an average volume of 1,600 cm^3.
The myth that humans only use ten percent of their brain is false. The folklore originated in an advertisement. In addition, the myth has been prolonged by those who profess psychic powers and others who promote supernatural powers.
Do the math in your head.
Take 1000 and add 40 to it. Now add another 1000.
Now add 30. And another 1000.
Now add 20. Now add another 1000. Now add 10.
What is the total?
The IQ quiz as we know today began with the Stanford-Binet test. Theodore Simon and Alfred Binet devised the IQ test in 1905. Their post test analysis was used to indicate a need for more teaching and didn?t necessarily imply an inability to learn. This philosophy is still held today with professionals and researchers.
Currently, the most common administered IQ test today is the WISC-IV test, the original WISC was developed by David Wechsler in 1974. The WISC methods test for ?Verbal IQ?, ?Performance IQ?, picture completion, coding, picture arrangement, block design, and object assembly. When all areas are completed a combined final IQ is determined, a strong emphasis is also placed on determining weak and strong areas.
IQ, an abbreviation for "intelligence quotient", is a score believed to measure general cognitive ability derived from a set of standardized tests. It is expressed as a number normalized so that the average IQ in an age group is 100 -- in other words an individual scoring 115 is above-average when compared to similarly aged people. The distribution of IQ scores is more-or-less Gaussian, that is it follows the famous "bell curve".
Modern ability tests produce scores for different areas (e.g. language fluency, three-dimensional thinking, ...), with the summary score being the most meaningless. It is much more useful to know which are the strenghts and weaknesses of a person than to know that he or she beats n percent of the populace in some "general intelligence" measure. Two persons with vastly different ability profiles may score the same IQ, but may exhibit different affinity to a given task, or may not be valued equally intelligent by other people.
IQ scores are sometimes proposed as an objective measure of intelligence, but of course a test encodes its creators beliefs about what consitutes intelligence. What various cultures dub "intelligence" differs. Most people also think that creativity plays a significant role in intelligence; creativity is almost unmeasurable by tests.
(The following numbers apply to IQ scales with a standard deviation 15.)
Scores between 90 and 110 are considered average -- so a person scoring 95 is simply average, not below-average. For children scoring below 80 special schooling is encouraged, children above 125 are "highly gifted". IQ scores outside the range 55 to 145 are essentially meaningless because there are not enough people to make statistically sound statements.