Dolphins and whales squeal after pleasant moments, researchers noticed long ago, such as receiving a tasty fish treat. A new study supports that these happy sounds are genuine expressions of delight.
The discovery, published in The Journal of Experimental Biology, not only helps to explain the meaning of these sounds but also provides evidence that dolphins and whales experience joy.
"We think we have demonstrated that (the squeal) has emotional content," said lead author Sam Ridgway, president of the National Marine Mammal Foundation.
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When human children - and some adults - squeal out of happiness there's a 100–200 millisecond delay from the time of the event and the happy sound. That's because the event prompts the release of a compound called dopamine in the brain.
Dopamine is a neurotransmitter that helps control the brain's reward and pleasure centers. Once dopamine is released, a person usually feels good and may get a boost of self-confidence.
Ridgway wondered if a comparable dopamine release delay - and the same brain reward process - happens in dolphins and whales.
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Delving back through decades of recorded experiments, he and his colleagues examined vocalizations of beluga whales and dolphins that had been trained to associate a whistle or buzzer sound with a food reward. Before long, the marine mammals seemed to become happy after just hearing the sound, with or without the food.
Measuring the time between the sound and the marine mammals' squeal determined that it was as expected, around 200 milliseconds on average.
"The dolphins take an average of 151 milliseconds extra time for this release, and with the belugas ... it's about a 250 millisecond delay," he said.
Photo: a beluga whale. Credit: Steve Snodgrass, Wikimedia Commons