> As I said before, the iq test mainly measures how much the participant is motivated... Or so many other reasons which are loosely correlated with professional success such as enjoying puzzles and figuring things out etc.

This is wrong, and somewhat obviously so. Most people taking an IQ test have never taken one before, and have no preparation. Some of the biggest IQ datasets come from military enlistees. If IQ were not correlated with nebulously defined "intelligence" and were instead some measure of "motivation" and "enjoying puzzles" we wouldn't expect to see it improve generationally with access to better nutrition and early-childhood education. We also probably wouldn't expect to see significant improvements from the introduction of iodized salt, which alleviated shortage of iodine, critical for early brain development, on a population scale.

"Iodine deficiency during development impairs motivation and enjoyment of puzzles later in life" is a much less plausible claim than "IQ correlates with what we commonly understand to be 'intelligence'".