As different people and you will get a different answer. Some say that IQ and age are not related variables. But you look at the data more closely and you can see that the answer is clearly “yes they can change – to some degree”. Children go through periods of very rapid mental development, so unsurprisingly, mental development and IQ can change year on year for young children. For Groups, IQs have been shown to be fairly constant from early adulthood through to adulthood (Salter 2008).
- The coefficient of correlation between IQ at age 5 and IQ at age 40 is 0.50-0.60 (i.e.55%)
- The coefficient of correlation between IQ at age 9 and IQ at age 40 is 0.70 (i.e. 70%)
- IQs at ages 10 &12 predict IQs at ages 17 & 18 at a correlation coefficient of 0.98 (i.e. 98%)