I think dolphins helped Nikki. But they, obviously, didn't teach him to speak. I think Nikki had a problem with his relations in the world, and he couldn't show his emotions. Contact with dolphins helped him to be more expressive.
I dont Know other stories about the therapeutic effect of animals, but I have information that nowadays many people use this therapy. Cats and Dogs, domestic animals have good effects with old people helping them don't feel alone.
I think that if you have a problem with your children and there is a possibility to solve it, you do everything that is in your hand.