I.Q., or intelligence quotient, is the ratio of the 'mental age' of a person to their 'chronological age'. I.Q. = 100 x M.A / C. A . For example, a 10 year old boy who has the intelligence of an average 13 year old boy, has an I.Q. of [100 x 13/10] = 130 . So, therefore, anyone with a mental age of 0, has an I.Q. of zero. Having a mental age of 0 would most probably be applicable to someone who is brain-dead, so during the history of man, i am certain that there have been countless cases of people with I.Q.s of zero.

An IQ of 0 is very hard to determine as the distribution of IQ scores is more-or-less Gaussian, that is it follows the famous "bell curve". The scores are adjusted based on average scores of a particular age group, thus IQ scores outside the range 55 to 145 are essentially meaningless because there are not enough people to make statistically sound statements. IQ is a difficult thing to measure as it isn't very clear what exactly Intelligence is: "If an IQ test is supposed to measure a person's intelligence, the question is: What is intelligence? Is it the ability to do well in school? Is it the ability to read well and spell correctly? Or are the following people intelligent? ---The physician who smokes three packets of cigarettes a day? ---The Nobel Prize winner whose marriage and personal life are in ruins? ---The corporate executive who has ingeniously worked his way to the top and also earned a heart attack for his efforts? ---The brilliant and successful music composer who handled his money so poorly that he was always running from his creditors (incidentally, his name was Mozart)? The problem is that the term intelligence has never been defined adequately and therefore nobody knows what an IQ test is supposed to measure. In spite of this the futures of thousands of children are determined by the results of this test. Already in the early 1920s the journalist Walter Lippmann maintained that IQ tests were nothing but a series of stunts. “We cannot measure intelligence when we have not defined it,” he said." Also, IQ tests have been proven to have unreliable results: "The unreliability of IQ tests has been proved by numerous researchers. The scores may vary by as much as 15 points from one test to another, while emotional tension, anxiety, and unfamiliarity with the testing process can greatly affect test performance. In addition, Gould described the biasing effect that tester attitudes, qualifications, and instructions can have on testing. In one study, for example, ninety-nine school psychologists independently scored an IQ test from identical records, and came up with IQs ranging from 63 to 117 for the same person." Above remarks in quotes are excerpts from: http://www.audiblox2000.com/dyslexia_dyslexic/dyslexia014.htm While I'm sure there has been at least one person born during the history of man that might have scored a 0 on an IQ test, given the controversy surrounding the testing and scoring of Intelligence, a score of 0 is suspect, at least in my mind.

Here is a table showing the probabilities of IQ's from 1 to 202. If I read it right, the probability of a 1 is less than 1 in 100 billion. As has already been mentioned, a 0 by definition indicates no mental activity, a vegetative state. So, while there are people whose IQ would be technically or effectively 0, they aren't actually capable of being tested or taking the test. http://members.shaw.ca/delajara/IQtable.html

I have never heard of anyone who would have such IQ! ButI have an IQ of 201!!!

Have you seriously read some of the questions and answers on here? Questions with very poor sentence structure and wrong or misspelled words? Answers that make no since and also have poor sentence structure and misspelled words? And especially those whom do not understand my answers or are willing to read or do any research on their own. There are many hidden thoughts and knowledge in my answers. So yes, I do think there are those on here whose IQ may well be “0”! Now don’t get all serious about my answer…some of it is tongue in cheek kidding, but also with some truth too.