Koda acts guilty if she does naughty as well
I agree with Taylor that they DO in fact recognize our facial expressions. I can give Koda a usual, cheery voice but if I look angry she won't come. If I look sad, she curls up to me and gives me love. If I look nervous she looks for what is bugging me. Same goes for any voice/facial expression combo. She watches my face more than she listens to my tone.