Dolphins squeal with delight
If you are familiar with the antics of Flipper or the charismatic creatures at Seaworld, this research is probably not going to shock you, but for Sam Ridgeway, a researcher who has spent decades studying these animals, it validates a suspicion he has had for years.
During the numerous experiments he conducted on dolphin behavior, Ridgeway often noticed that his animals seemed to emit little cries after receiving a treat. These cries sounded remarkably similar to a child’s squeal, which prompted him to name them “victory squeals.” Scientists liken these sounds to a bat’s feeding buzz, which is a series of echolocation pulses used to locate and capture prey. Dolphins and whales have their own version of a feeding buzz, increasing their squeals as they hone in on a meal. Unlike bats however, they don’t stop when the meal is over. Ridgeway suspects that the timing of their cries signals an emotional expression.
In order to support this hypothesis, he analyzed decades of research looking to find a correlation between the timing of the squeal and the release of dopamine, which signals pleasure in the brain. In terrestrial animals, who have well established dopamine reward systems, it takes about 100-200 ms after a reward for dopamine to be released. Ridgeway postulated that if the delay between the reward and the victory squeal was longer than the dopamine release timing, then the cries could indicate emotion. His careful analysis showed that dolphins emit a victory squeal on average 150 ms after a reward, and whales an average of 250 ms. “We think we have demonstrated that it [the victory squeal] has emotional content,” he said about the results.
His research will be published in the Journal of Experimental Biology today, August 13, 2014. To read more see the original research:
Video credit: US Navy