"Tolerance of ambiguity" is a new phrase for me. Thanks for writing about it.

Nevertheless, I wonder if its correlation with adult language learning is indeed causation, or if it is the other way around: people who tolerate ambiguity don't hesitate to learn a foreign language.

Case in point: even from a young age, I've always been a carefree reader of quantum physics, mathematics, horticulture, and other topics, even though I don't understand many of the words or concepts. And now that I'm aging, I don't hesitate to pick up academic research papers filled with strange medical jargon. So, I'm clearly a person who tolerates ambiguity.

I'm a native English speaker, with speaking level comfort in Japanese, and I find it stimulating to watch subtitled, foreign language television.

So, correlation yes, but causation?