Anyone who owns a bird doesn't need a scientist to tell them how incredible and incredibly smart they are. So smart, they even have personality quirks like many humans do.
Pako has 1 feather he plays with and will hand to you. We call it his feather friend. He registers "Step up" the more commanding the tone, the faster he'll step up, even if he doesn't want to. He knows "Go poopy" and he will because he knows he won't go back on your shoulder until then.
Georgie is afraid of hands and extremely attached to his 2 yarn toys. Aptly named his wife and his mistress. Registers, "Wanna cuddle?" and if he's in the mood, he'll launch into the blankey for cuddles.
For those who don't understand, here's some sites and videos! Learn why Bird Brain is a compliment.