No scientifically recognized record exists for the highest IQ ever recorded. Several exceptionally high scores have become famous, but extreme results are difficult to compare because intelligence tests are not designed to measure tiny differences at the upper limits of their scales.
Among the most frequently cited cases is journalist Marilyn vos Savant, who was attributed an IQ of 228 at the age of 10. Mathematician Terence Tao has also been linked to estimates between 220 and 230, based on tests taken during childhood.
Both figures require caution. Vos Savant’s score was calculated using the ratio-IQ method, which compares mental age with chronological age. This approach is now considered unreliable, particularly when applied to extremely high values. Tao’s estimate, meanwhile, is an extrapolation from results obtained when he was a child.
Tao himself has played down the higher figures, saying that a score above 175 is a more plausible assessment because intelligence tests become increasingly imprecise beyond certain levels.
IQ scales are mainly designed to distinguish most of the population, not to accurately rank a very small number of people with exceptional results. For that reason, psychologists generally prefer to refer to exceptional cognitive abilities rather than identify an absolute IQ record.
Sources: Focus.it.