In all other regions the dolphins are comparable to us with some differences. Their visual system is one-tenth the speed of ours; however, they make up for this in that their sonic and acoustic systems are ten times the speed of ours, This means tht the dolphins can absorb through their ears the same amount of information—and at the same speed—that we do with our eyes. We can absorb through our eyes ten times the amount of information that the dolphins do through theirs.
This means that we are dealing with a species that is primarily acoustically oriented. We are primarily visually oriented. Our visual orientation is built into our language so that we, in general, talk as if we were watching and seeing and analyzing what we were talking about as if seen.
In contrast, the dolphins “see” with their sound-emitting apparatus and the echoes from the surrounding objects underwater. Remember that half the twenty-four-hour day, during the night, their eyes do not need to function. Remember that they must be able to “see” underwater in the murky depths during the day as well as during the night. They must be able to detect their enemies, the sharks; they must be able to detect the fish that they eat; and they must be able to detect one another in spite of a lack of light; therefore, they have an active processing mechanism for sound that is immensely complex.
Over the years we have examined the sound-emitting apparatus of the dolphins very carefully, both anatomically and physiologically. As is presented in The Mind of the Dolphin, they have three sonic emitters, two of them (nasal) on their forehead, just below the blowhole, anterior to the brain case. They have their third one in their larynx, which crosses their foodway in the nasopharynx.
…This is a very sophisticated system with which the dolphins can get not only the distance of objects, but also the composition of those objects in terms of density. They emit this (sonic) beam and scan one another’s bodies. If one gets into a pool with them, they immediately turn on their sonar and scan one’s body. This is one of their forms of recognition for individuals. (They can also recognize one visually under well-lighted circumstances.)
This sonar beam can penetrate one’s body, is reflected off one’s lungs, the gas in one’s gut, and the air cavities in one’s head. A dolphin looking at one’s stomach, for example, can tell if one is anxious or upset because the stomach tends to churn during anxiety. They can see this churning with the bubble of air that is in the stomach.
…With such a degree of sophistication of their emitters and an equal sophistication of their receivers, their ears buried inside their heads, they can do amazing things with this apparatus.
For example, a dolphin can distinguish the difference between a one-inch diameter, one-sixteenth-inch thick aluminum disc against a concrete wall versus a copper disc of the same dimensions, when this is hidden behind a visually opaque but a sonically transparent screen.
Two dolphins communicating sound like three dolphins. They may face each other and use the laryngeal tight sonar beam for communication when they do not want somebody else to know about their communication. We often found them doing this in our laboratory, and every so often we had the opportunity of having a hydrophone between them and we would then detect the fact that they were doing this. We could not hear it of course, it was too high a frequency for our ears, but we could show it on a cathode-ray oscilloscope and record it on high-frequency tape recorders.
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