&gt; I feel like the whole argument is based on &quot;your true IQ is the highest score you&#x27;ll ever receive on a test&quot;, which is a statement that by definition would make improvements in IQ impossible.<p>I am no statistician, but I think there is more to the argument than that. My take is that Haier is saying that IQ is not a ratio scale, and you cannot gauge the significance of a result by treating it as if it is.<p>Nevertheless, I get the impression he is trying to stretch the importance of this observation. He writes &#x27;Nonetheless, the main point is that to make the <i>most compelling</i> argument that intelligence increases after an intervention, a ratio scale of intelligence is required&#x27; (my emphasis), which raises the question of whether there is not a not-quite-so-compelling argument to be made without such a metric.<p>FWIW, I don&#x27;t have a horse in this race as I am on the fence over whether IQ is as fundamental a measure as its proponents insist.