There have been two interesting studies that further support the hypothesis of somewhat complex communication system. One was done in Florida with wild dolphins who hunt cooperatively. One dolphin drives the fish,while others act as a barrier. Such cooperation requires sophisticated acoustic communication. Another study was an experiment with dolphins in managed care. Dolphins were asked to push two separate buttons at the same time, but they could not see each other. So they had to communicate acoustically to achieve the perfect timing and push the buttons together.