What is the lowest IQ score in history?

Answer 1

For the real answer, look here:

It would be extremely unethical for a person's IQ score to be revealed in a public forum like this. IQ scores are considered to be confidential. I can say the bottom or 'floor' of most standardized IQ tests (not that made up online crap) is an IQ of 20 or so. Adaptive behavior ratings scales can go lower, but there's really no point, because once you get to IQ's that low, there's virtually no real difference in performance. The lowest IQ I've ever gotten was for a kid with a 'smooth brain' meaning she had no wrinkles in her cerebral cortex, meaning no learning could take place. Since the processes that automate breathing and regulate autonomic functioning develop first, she could do that independently, but that's about it. So I had to administer the Developental Profile, which is a way of measuring cognitive ability by asking a caregiver questions about the person. The child at the age of 9 had the mental capacity of a 1 month old child, as she couldn't orient toward sound, roll over, etc. If that child is still alive, she would be about 18 now, and probably hasn't gained any skills. However, because she is at the bottom, her IQ would not change, even though she is further behind her peers than she was at 9.

I will say I've seen psychologists mess up and do the calculations wrong and give a child a negative IQ score! There is no rational '0' when talking about IQ scores, so a negative score makes no sense. We all laughed at that, it's not statistically possible!

Source(s):School psychologist who has administered hundreds of standardized (formal) IQ tests, even to those who were severely cognitively delayed.