Cetacean intelligence
The Dolphin Brain is similar in size to the human brain (slightly larger in some, up to 5 times larger in others, like the Orca, but their brain to body ratio is slightly lower than humans on average. Their brain consists of two hemispheres divided into four lobes—very different from the human brain. It is unknown why dolphins evolved this structure. Some hypothesize that the dolphin brain is shaped this way to allow for more acute conscious perception of three dimensions, thus allowing it to use its highly developed powers of echolocation. Others have gone as far as to say that dolphins perceive higher dimensions of reality than humans do. It appears that dolphins are an example of highly evolved oceanic intelligence. It has been long-theorised that they have a complex language, which may consist of visual symbols as interpretations of high frequency sound waves.
Dolphin brains and Human brains are similar in size, but somewhat different in structure. Human brains appear to be composed of two mirror-symmetric dissimilar hemispheres. Dolphin brains appear to be composed of two similar sub-brains, each of which has two hemispheres, so Dolphins might be said to have 4-lobed brains.
Dolphins may need to have 2 brains because the maximum size for a single brain may be about 10^11 neurons, the size of the brain of single-brained humans. According to Carol J. Howard, author of Dolphin Chronicles (Bantam 1996), each of the two Dolphin sub-brains has an independent blood supply.
Dolphins never sleep with both brains at once. One brain sleeps while the other brain stay awake (perhaps so that the Dolphins can breathe while asleep). Dolphin sleep appears to be different from human sleep in another way: the brain waves of sleeping Dolphins have no state that corresponds to the rapid-eye-movement REM sleep of dreaming Humans.
Dolphin brains are more convoluted than Human brains, but the cortex of Dolphin brains is thinner than the Human cortex, so that the total mass of the Dolphin neocortex is slightly smaller than the mass of the Human neocortex.
Dolphin brain cells appear more uniform and less specialized than Human brain cells.
Dolphins are born with about 40 percent of their brain mass, and reach full brain development in about 10 years, while Humans are born with about 25 percent of their brain mass, and reach full brain development in about 18 years.
The two eyes of the Dolphin are each connected to one of the two sub-brains.
The Dolphin brain area for visual imaging is only about one-tenth that of the Human brain, while the Dolphin brain area for acoustical imaging is about 10 times that of the Human brain.
Dolphins not only have two sub-brains, but they also have two sets of sound-pruducing organs, including two "tongues" on each side of their blow-hole. Therefore, Dolphins can produce two independent sounds, from their right and left sides. They can use interference to focus sounds and to produce harmonic interference effects. Two Dolphins speaking can sound like four.
In front of the Dolphin blow hole is the melon, a lens of fatty tissue, corresponding to the Human upper lip. The melon may act as a lens to focus sound, or to send or receive ultra low frequency sound waves. According to a 1 February 2001 article in the Electronic London Telegraph by Robert Uhlig: "... New Scientist reports ... Dolphins use sound booms and clicks to stun and kill their prey ... In one study Ken Marten of Earthtrust, a conservation group in Hawaii, recorded a dolphin emitting a sequence of low-frequency "bangs" while pursuing a fish. ... Denise Herzing, of Florida Atlantic University, recorded wild Atlantic spotted dolphins emitting a medium-frequency buzz while searching for prey on the seabed. She said buried eels jumped out of the sand, and either stopped or moved sluggishly as if stunned, giving the dolphin time to catch them. ...".
Dolphins can create air bubble rings and helices in water.
Dolphins may be able to use focussed sound to produce cavitation. Evidence please
Cavitation in biological tissue could produce sono-chemistry, sonochemical changes at cellular boundaries in living tissue, that may explain some chemical and electrical changes that have been observed in Human brains after contact with Dolphins.
AquaThought Foundation and David Cole have found that after Humans been in contact with Dolphins, the dominant Human brain frequency drops from beta to alpha, closer to the frequency of the Schumann resonanaces of Earth, and the hemispheres of the Human brain become synchronized, in that brainwaves of the left and right hemispheres are in phase and of similar frequency.