WASHINGTON: Dolphins often squeal when they get a fish treat, sounding much like happy children.
US researchers said on Wednesday they believed these calls are not just ways of signalling to others in the group that there is food around, but expressions of pure delight.
The reason they think the dolphins’ sounds indicate pleasure is they match the amount of time it takes for the brain to release the hormone dopamine.
The study in the Journal of Experimental Biology was led by Sam Ridgway of the National Marine Mammal Foundation in San Diego, California. Ridgway and colleagues work with bottlenose dolphins and beluga whales, training them to repeat behaviours and rewarding them with fish.
Previous research has shown that rats and primates have reward systems involving dopamine neurons.
Ridgway and colleagues found that the time delay between the pleasant experience — the reward, or expectation of reward — was just a bit longer than the time it takes for the dopamine release, usually around 100 milliseconds. “The dolphins take an average of 151 milliseconds extra time for this release, and with the belugas it’s about 250 milliseconds delay,” said Ridgway.
AFP
