yes, they're very smart.
My interactions with my nephew's turtle has been amazing!
I helped take care of the turtle whenever I visit my brother's house, as my nephew neglect it most of the time...
recognized me, and will respond to my callings.
She is very curious too, likes to "spy" and watch what I'm doing. When you look at her, she will turn her head and face the wall. LOL.
She recognize food containers' colours and shapes, when she saw things resemble it, she will swim towards it thinking there's food.
When I try to take a picture of her, she seems to always able to look at the camera, as if she just know where the lens is???
Damn smart.