The happy sounds of dolphins

Research has found that when dolphins squeal, they are actually expressing delight.

Dolphins often squeal when they get a fish treat, sounding much like happy children. US researchers says they believe these calls aren't just ways of signalling to others in the group that there's 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.