Dolphins squeal with delight
15 August 2014 Last updated at 17:25 BST
A study of trained dolphins has suggested that the marine mammals express pleasure with squeals of delight.
Researchers first noticed these squeals when they rewarded the animals with fish for successfully completing tasks.
A new study published in the Journal of Experimental Biology reveals that these squeals occur after the length of time it takes for a chemical called dopamine - associated with feelings of reward - to be released in the animals' brains.
This footage, shot from the viewpoint of a dolphin, shows the animal catching a fish and emitting one of these squeals.
Footage courtesy of Sam Ridgway, UCSD