In one Lilly experiment, a woman lived in a pool with a bottlenose dolphin named Peter as her only companion for several months. Sleeping in a bed above the pool, she was ever on call. Communication attempts were often transing sessions, where the woman attempted to teach language to the dolphin. Peter was reportedly a demanding 'roommate', and the woman eventually withdrew from the project. While a basic communication did develop, reportedly similar to that between a dog and a human, deeper exchanges - of dolphin whistles or human words - did not occur.
Lilly's work ended in the 1980s. Since then, researchers led by Louis M. Herman have developed a new approach to communication studies with captive bottlenose dolphins at the University of Hawaii. Their goals have been to discover how dolphins process information, both through sight and sound, how they learn and how they communicate. Herman's research has verified earlier findings that dolphins have good memories and can mimic a wide variety of sounds. Able to store new information, they can also update old information rapidly.
In one experiment, Herman played up to eight different short sounds on an underwater speaker in the dolphin's tank. Then another sound was played, sometimes one of the previous eight, sometimes an entirely new sound. The dolphin had to decide whether it had heard the sound before. About 70 percent of the time, the dolphin responded correctly. If the list was shortened, however, to one or two sounds, the results were 90 percent correct. Like humans given such tests, the dolphins found the recent items easiest to remember.
The dolphin's most impressive accomplishment is its ability to understand sentences expressed in either an artificial acoustic or a visual language. In the experiments, the "words" of the language are sounds generated by a computer and broadcast via an underwater speaker. First the dolphin learns words such as fetch, ball and hoop. The words refer to (1) objects in the tank; (2) actions that might be taken in connection with the objects; and (3) modifiers of place or location. In "sentences" of two or more words, the dolphin is then told to do something. The level of understanding is measured by the accuracy and reliability with which the dolphin carries out the instruction.
Dolphins perform very well on such tests. To more than 600 two-word sentence instructions, the dolphins gave correct responses about 80 percent of the time. They also understood "new" instructions almost as well as familiar ones, with only a slight advantage to the familiar. New instructions consisted of fresh combinations of words that either obeyed the language rules or, in a few cases, were logical extensions of existing rules.
Gradually, the dolphins seemed to master sentence form and use. They were taught to respond to sentences up to five words long. Then visual symbols or gestures, as well as auditory signals, were tried. Comprehension for a dolphin trained with visuals was the same as that for a dolphin trained with sound.
These and other experiments show that dolphins can learn rules and understand certain abstract concepts. And they can work with both auditory and visual symbols. Compared with apes taught to use America sign language - an exclusively visual medium for communication - the dolphins have more range. The apes, on the other hand, learn more quickly in tests involving symbols. Of course, all of these are laboratory feats and prove nothing about life in the wild - for dolphins or apes.
Herman and other researchers, however, believe the society of the wild bottlenose dolphin is a socially dependent world in which learning everything about the other members of a group may be crucial for survival. Within these dolphin societies, says Herman, social rules or conventions that may be complex might govern social relationships, social roles and social behaviors.
In the future, trained dolphins may be able to grasp more complex human-taught vocabularies. But this does not necessarily mean that dolphins have their own language. We cannot know where research will lead. Many scientists feel that we can only glimpse what really goes on inside the mind of a wild dolphin.