Dolphins get rewards when they achieve their goals.
When training a dolphin, the specialist must condition the animal to accept different types of human touch. The animal is then rewarded for “not moving away” from this touch.
But why would the dolphin want to follow a target? - Simple: They teach the dolphin that if it follows the target correctly, it will get a reward. The first behavior we actually train is targeting. We place a target, such as a small float on the end of a pole, on the dolphin's rostrum, blow the whistle and give the animal a reward. We repeat this several times. The next time, we place the target a short distance form the dolphin's rostrum and wait. Because the animal has been rewarded for touching it in the past, the animal makes the mental leap and moves to touch it's on his own.
Now that we have trained our dolphin to target, we can train any behavior. Trainers use their hands (and sometimes target poles) to help guide an animal's movement and direction. A signal is incorporated at the very beginning of the training to denote that particular behavior. Each behavior must be given a new distinct signal so as not to confuse the animal with something it may already know.
Putting the signal in right at the start of the training has a few benefits. It allows the animal to link all the steps it knows for one behavior to one signal. It allows the animal then to show the trainer what it knows well and the trainer can then add the next step.
Finally, the signal allows the dolphin to work on different behaviors with different trainers instead of learning only one behavior at a time. By the time the trainer gets to the last step in the training, the animal will be able to do the whole behavior just on the signal alone.