Dolphins are believed to be intelligent and second in smartness next to humans. However, some scientists claim that dolphins are not as smart as was previously thought.

Dolphins are cetaceans, mammals that live in water bodies, and are found worldwide. John Lilly, an American physician, neuroscientist, writer, philosopher and a dolphin researcher, popularized the notion that dolphins were intelligent. He later claimed that dolphins were even smarter than humans. Lilly wrote 19 books, some of them related to dolphins, and also tried to make interspecies communications between dolphins and human possible.

Lilly tried to teach computer language to dolphins in an attempt to develop a common language between humans and dolphins. His research on dolphins suggested that the sea mammals could recognize symbols, recognize themselves in the mirror and identify their body parts. Dolphins' large brains were believed to make them smarter and more intelligent than other species.

However, recent studies suggest that dolphins are not as smart as thought by many scientists. Paul Manger, an anatomist and researcher with the University of the Witwatersrand in South Africa, reveals that the large brain of the dolphins helps them retain heat and has nothing to do with intelligence.

"Sophisticated cognitive abilities appear to play no role in the evolution of large brain size in cetaceans, indicating that alternative theories of large brain size evolution in cetaceans should be considered in more detail," says Manger in one of his studies.

Manger also reveals that the intelligence of cetaceans is qualitatively similar to other vertebrates.

He stated that sea lions can learn to recognize symbols more quickly than dolphins, but they have never been treated as being more intelligent than dolphins.

Researchers also reveal that dolphins show the same behavior in the presence or absence of a mirror. Manger believes that this behavior suggests that the dolphins cannot recognize themselves in the mirror.

Justin Gregg, a researcher and author of the book "Are Dolphins Really Smart?," also suggests that while dolphins show many cognitive behaviors, some other animals also have similar abilities.

Both Gregg and Manger believe that dolphins are not as special as many people believe and they are at par with many other animals.