For many years, psychologists have been aware of practice effects: improvements in performance on tests as a result of increased practice on the tests ( 8 ). Historically, practice effects have been viewed somewhat negatively, as though there’s something wrong with a test on which one’s performance would improve with practice. On the contrary, however, almost any skill will improve with practice, and there’s no reason to believe that the cognitive abilities measured by IQ and related tests would be any different ( 3 ).
There used to be a misguided view that improvements in IQ and related cognitive skills were inherently at odds with the belief that intelligence is partially heritable. Nothing could be further from the truth. Average heights in the United States have increased greatly from our parents’ and grandparents’ generations although height is among the most highly heritable of physical traits (with a heritability of about .9, higher than any psychologist has claimed for intelligence). So heritable traits are not necessarily fixed traits.