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Actually the jury is out on this one. Average intelligence levels, as measured by standardized intelligence tests, have been rising since at least the early 20th century. A recent meta-analysis that included more than 4 million people in 31 countries found an average gain of about three IQ points per decade, or roughly 10 points per generation. Another recent study found a similar increase.



The phenomenon is commonly called the “Flynn effect,” after James Robert Flynn, the New Zealand academic who documented it in a series of studies starting in the early 1980s. The rise in IQ has been found in both developed and developing countries, but it varies by degree across countries, over time, and according to the type of intelligence measured. The Flynn effect has been stronger for nonverbal tests than for verbal ones, for instance, and greater for adults than for children. But more recent research has shown that rises might be levelling off, or even that the effect is questionable.

 www.ncbi.nlm.nih.gov/pubmed/25987509