Raw IQs have been steadily increasing for decades, and IQ tests have been renormed along the way, but this Flynn Effect has been more pronounced in the more abstract, less culturally loaded sections of the test:
The kind of cognitive facilities that come up in normal conversation, such as vocabulary, arithmetic and general knowledge, have only seen small Flynn Effects, which is why the Flynn Effect isn’t easily noticeable in much of daily life (although I’ll point out below where it can be seen).
One of the big changes in daily life over recent centuries has been the growth of what I might call humans having to deal with “machine logic.” People today deal far more often each day than in the past with semi-intelligent machines who can only be dealt with in a certain way according to their logic. You deal with the ATM rather than with a bank teller, with a gasoline pump rather than with a pump jockey, with elevator buttons rather than with elevator operators. You can’t wave your hands around with these machines until they figure out what you want done. You have to follow a precise logical series of steps.
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Generation after generation, children grow up in an environment ever denser with the kind of systems logic that the more Flynn Effected-Wechsler subtests ask about. Growing up, kids these days get more practice with the kind of thinking tested on the Raven’s and on some of the Wechsler subtexts. And they legitimately are better at it.
The Flynn Effect is a side effect of the developers of the IQ test being on “the right side of history.”