A reinforcer is anything that increases the frequency of behavior. Trainers use several tools to help them work with the animals. The term bridge is used to describe the stimulus because it bridges the gap between the behavior and the reinforcer. This immediate feedback is important because the animal may be in the water far away from the trainer and needs to know which behavior was correct. With marine mammals, a high-pitched whistle is often used as a bridge because it can be heard above or below water and is always the same.
Consistency is important.
The animal has learned that a whistle means it has done something correctly and that it can expect a reinforcer of some sort. Another training tool is a target. The target is usually either a trainer's hand or a small ball at the end of a pole. The ball acts as an extension of the trainer's hand. Most often, animals are trained to touch the target with their nose or mouth.