The creatures have long since been thought of as the most intelligent of animals and a new study has found their brains are second only to humans in size.
Lori Marino, a neuroscientist at Emory university in Atlanta, US, will tell the American Association for the Advancement of Science (AAAS) conference their high intelligence means they can suffer psychological problems linked to being captured and confined.
She said dolphins could be traumatised by being kept in a theme park or by swimming with tourists.
Dr Marino said: “Our current knowledge of dolphin brain complexity and intelligence suggests that these practices are potentially psychologically harmful to dolphins and present a misinformed picture of their natural intellectual capacities.
“Dolphins are sophisticated, self-aware, highly intelligent beings with individual personalities, autonomy and an inner life. They are vulnerable to tremendous suffering and psychological trauma.”
Source: The Telegraph