For the past 50 years, Sam Ridgway, a marine biologist and the president of the National Marine Mammal Foundation, has worked closely with dolphins and whales and whenever he would reward the cetaceans he studied with fish, they would let loose an audible squeal. At first, Ridgway believed this squawk was a signal to other mammals that food was nearby. But a recent study published in the Journal of Experimental Biology indicates that dolphins and whales aren't simply calling out, "Hey, here's fish!" - rather, the cetaceans' squeals are sounds of delight.
"We think we have demonstrated that [the squeal] has emotional content," says Ridgway in a press release.
The trick was timing the squeal with the release of the dolphin dopamine. Dopamine (once called "the Kim Kardashian of neurotransmitters") surges in anticipation of a reward, but there's a delay as the brain processes hearing or seeing a reward. If the cetacean vocalization came after the delay - about 100 or 200 milliseconds - then the sound would be closer to a giggle than a shout.