I may also try dual N-back testing to quantify the effect but am open to other suggestions

N.B. for self-experimenters: bullet chess and three minute blitz chess are very, very useful for quick, fun cognitive testing once you're beyond ~1400 Elo and aren't improving rapidly. If you're attentive not only will you notice overall performance changes, you'll notice changes in various subskills, some of which I strongly suspect have transfer with rationality subskills. (Not enough time to justify that claim here.) Whenever I try a new drug or am just feeling different for some unknown reason I'll play at least five games of blitz to figure out more precisely what's different about my mind.

(N-back works too of course but is relatively aversive and doesn't factorize into subskills as introspectively-obviously as chess does. But that could very well be because I never got beyond 4-back whereas I've played a lot of chess.)