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Dolphins and whales squeal with pleasure when they are particularly pleased, according to scientists, Sky News reports.

The connection with emotion was identified in a study when scientists offered the mammals tasty fish treats.

Initially, the researchers thought the squeal was a communication to others indicating the presence of food.

But the new research seems to indicate that the squeal is, quite simply, a cry of delight.

The experiment was headed by Dr Sam Ridgway, president of the US National Marine Mammal Foundation and the results produced in the Journal of Experimental Biology.

It worked on the basis that whales and dolphins are known to squeal when they hear a whistle or buzzer that is associated with a food reward.

In the experiment, the dolphins and beluga whales were trained to switch off a sound after making a deep dive and they produced the same squeals as if to announce a satisfactory outcome.

It was the equivalent of a human cheer, Dr Sam Ridgway, a US cetacean expert said.

"The (squealing) behaviour had transferred over to another stimulus that wasn't food," he said.

To investigate further, he and his team analysed decades of recordings of experiments involving dolphins and beluga whales to see if a delay before a squeal indicated the release of dopamine, a brain chemical that stimulates sensations of pleasure.

The scientists allowed for a period for the dopamine to take effect, concluding that if there were sufficient delay between a reward and a squeal, it would suggest an emotional response.

That proved to be the case.

"We think we have demonstrated that it (the victory squeal) has emotional content," said Dr Ridgway.