I'll take issue with this quote: "This is a problem because research has shown that the excitement and fun induced by novel activities can cause a positive temp

I'll take issue with this quote: "This is a problem because research has shown that the excitement and fun induced by novel activities can cause a positive temporal effect on test scores - a placebo effect." This is not a placebo effect. Doing a variety of things does make you smarter. If I learn to play chess, there is a very real effect. From there, you have diminishing returns on investment. If I play chess for 4 hours per day, then it crowds out other, more productive activities. There is a perceived mystique to chess, but it's no different then checkers, contemporary German game geek games, or any of a range of other strategic games. People who play such games a lot will be better players when placed in a novel game (or a real-life situation which requires the same type of strategic thinking). And such games are no different than a broader set of other cognitively-engaging activities, be that logic puzzles, editing Youtube videos, or STEM/maker activities. In most activities, there's an initial surge of growth (so long as I do it for long enough to learn something -- not a one-hour thing I forget after a few months), followed by rapidly diminishing returns, but that's far from universal. In programming, for example, that surge comes when people start to think algorithmically (e.g. in terms of big-O notation), not when learning to order operations. In reading/writing, that comes when people start to really think through audiences, structure of text, etc.