You bring up some interesting points.  But, (I am not an expert in psychology), my understanding of the article is precisely that intelligence can be reliably increased in the long term.<p><i>EDIT: Also note that the researchers point to increased grades - not increased IQ scores.</i><p>You are quite correct, however one would hope that grades have at least some correalation with intelligence, but more importantly they are the measurable results in school.  Being able to increase those measurable results is the primary goal, even if hypothetically intelligence did not go up.<p>I have been told that in weightlifting the first several stages do not increase the amount of muscles, but they help you call on that strength better so you can lift more and get tired more slowly.  This increases your effective abilities even if you do not develop more actual muscle right away.<p>Similarly, if the ability to use their intelligence is increased hypotethically without actually increasing the intelligence itself, this is still a major improvement.