It had been just the subtlest shift. Donnie's no expert on emotions and feelings, that's his little brother's territory, but when he's paying attention, he can at least notice some differences, even if he has no idea what they may mean. Machines are so much easier to decipher.

"Ah," the turtlekin says once Rezo replies, nodding a little and accepting the answer for what it is. It makes plenty of sense to him, anyway.

His smile is lopsided on the following note, prompting a laugh. "Probably not, which I guess would be good and bad since it wouldn't be the best gauge to know if you were improving. Well, I'll keep an eye and ear out for anything, if you'd still be interested. Anyway, should I leave you to the books or is there anything else you wanted to look for?"