A Research Compilation
By George Walter
Dr. Poorna Pal
Oceanography 115
July 27th, 1993
DOLPHIN INTELLIGENCE
Dolphins have the highest encephalization quotient of any non-human animal- twice that of higher primates.Footnote1 The Encephalization Quotient is the ratio of brain mass to body mass, and is a better indicator of brain power than brain size alone. In addition the bottlenose dolphin's brain is more convoluted (physically more folded) than that of any other mammal, including humans. Its cerebral cortex, however, is only half as think as a humans, but thicker than a chimp's.
In addition to the physiology of their brains, the dolphins show abilities extremely rare in the animal kingdom. Besides humans, only dolphins have demonstrated the abilities of both vocal and motor mimicry.Footnote2 Birds can do vocal mimicry, but not motor. Monkeys are good motor mimics, but are not capable of vocal mimicry.
Dolphins use a wide variety of hunting styles to catch a wide variety of fish and invertebrates. Fish kicking, the technique of hitting with the tail a fish which has turned quickly to avoid capture is a local custom among dolphins and appears to be a learned behavior rather than instinct. One very interesting example involves two captive dolphins intent upon extracting a moray eel from a rocky crevice in their tank. One of the dolphins captured a scorpion fish and, with the fish in its mouth, poked at the eel's rear end with the fish's poisonous spine. The moray fled from its haven only to be captured by the second dolphin stationed at the opposite end of the hole.
In discussing dolphin intelligence, Louis M. Herman, Director of the Kewalo Basin Marine Mammal Laboratory, of the University of Hawaii, feels that a significant point is that "the dolphin is capable of remembering totally arbitrary events of no relevance to its natural world, of no relevance to what's biologically important. And it can report its memory in ways that are totally arbitrary, that are not the natural conventions of the species", in contrast to wasps and bees, which do demonstrate memory, and even communication of this memory (in the case of the bees' nectar dance), but only in very restricted, biologically set ways.Footnote3
Many humans find the idea of communicating with other species intriguing. It is the intelligence and abilities, along with the high degree of socialization, of the dolphins that have made them attractive as subjects for animal language research.
LANGUAGE RESEARCH WITH DOLPHINS
Neurologist John Lilly pioneered the acoustical study of cetacean vocalizations in the 1960's. As Lilly continued his research through the sixties, he became less and less conventional in his approach. He tested the effects of LSD on dolphins' vocalizations. Lilly's work stopped in 1969 after five of his dolphins mysteriously 'committed suicide' within a two week period.Footnote4
During his research, many of Lilly's findings and claims were not backed up with significant data and his credibility, and that of animal language research, suffered. As a result, todays research in this field is rigorously controlled and meticulous, and interviews and predictions with today's researchers in the field seem very reserved and measured.
Louis Herman is perhaps todays foremost researcher studying communication and cognitive abilities in dolphins through using artificial languages (i.e. simple languages created for the research). He has focused on language comprehension rather than production, because comprehension is the first sign of linguistic competency in young children, and because comprehension can be tested in a more controlled manner than production.
In Herman's work, two dolphins, Akeakamai (Ake), and Phoenix, were taught artificial languages. Phoenix was taught an acoustical language made of computer generated sounds. Ake was taught a gestural, or visual, language. The signals of the artificial languages represent objects, object modifiers, or actions. Neither the gestures nor the sounds resemble the objects or relational terms to which they refer. The languages also use syntax or simple grammar rules, meaning that the word order effects the meaning of the sentence. Phoenix was taught a straightforward left-to-right grammar. Ake's gestural language grammar is inverse, requiring her to view an entire gestured sequence before it can be interpreted correctly. For example, in Ake's gestural language, the sequence of signals PIPE SURFBOARD FETCH means bring the surfboard to the pipe, and SURFBOARD PIPE FETCH means bring the pipe to the surfboard. Phoenix and Ake have each learned approx. 50 words, these 50 words allow more than 1000 different 'sentences', each eliciting an unlearned, unrehearsed response. To minimize any possible effects of orientation to space or person on dolphin learning, stations and trainers are changed from session to session. Blind observers, people who do not know and can not see the commands given, are used to label the actions they observe the dolphins perform as a means of comparing objectively the response to the command.
Trainers wear dark goggles, maintain expressionless faces, and hold their bodies steady during formal training sessions. Dolphins can understand gestural signals given by televised images of signers about as well as they can from live signers. Even just showing white hands in black space, or white spots of light tracing out the dynamics of the gesture, were understood. Because of these experiments, it seems that the dolphins are responding to the abstract symbols of the language rather than to any non-language communication or cues.
In addition to following the language instructions, Herman's dolphins can now correctly answer whether a specified item is present or absent by pressing the appropriate paddle (the white one for yes, or present, and the black one for no, or absent). This demonstrates the skill of displacement, the conjuring of images that are not around. It has been similarly demonstrated by Sue Savage-Rumbaugh, of Yerkes Primate Research Center, that apes are able to understand a reference to something that is not in their presence.
Additional experiments have been conducted to determine how the dolphins are interpreting the language labels. "We did test to see, for example, what a hoop is to a dolphin. A hoop is not just the hoop used in training the animal. It's anything with an opening in it, relatively large to its perimeter. So we have round, square, and little hoops; hoops that float and hoops that lie on the bottom."Footnote5
Things Herman has been unable to successfully teach the dolphins includes the concept "not" as a logical modifier, so that jump over "NOT BALL" would indicate jump over anything but a ball. Also large and small do not seem to have been understood by the dolphins.
Data acquired from whale vocalization studies was practically applied to save a young whale when Herman provided a recorded whale feeding sound that was used to successfully lure Humphrey, the humpback whale who had swam more than fifty miles up the Sacramento river, back to the open ocean.
Says Herman, "We now ask, `Is there a frisbee in the tank?` It's not much of a stretch to say, `Is there a whale out there? A submarine? What's on the bottom?`"Footnote6
NATURAL DOLPHIN COMMUNICATION
Dolphins produce many whistles. The function of many dolphin whistles is unknown, but, at least half the whistles that each dolphin produces are signature whistles.Footnote7 A dolphin's signature whistle ranges between 5 and 20 kilohertz and last about a second. It is distinguished from the whistles of the other dolphins by its distinctive contour, or frequency variation over time, as revealed in sonagrams. Calves appear to develop their own signature whistles between about two months and one year of age. These whistles remain unchanged for at least 12 years and quite likely through the animal's lifetime.Footnote8
In addition to making their own signature whistles, some of the other whistles dolphins make are precise imitations of the signature whistles of companions, which appear to be for calling one another 'by name'.Footnote9
Psychologist James Ralston and computer specialist Humphrey Williams have found that the signature whistle can convey more than just a dolphin's identity. By comparing sonagrams of the dolphin's signature whistles during normal social activities and stressful situations, they found that although keeping its general configuration, a signature whistle may change in pitch and duration, conveying information about the emotional state of the animal. Footnote10 The variation due to emotional states on intonations of the signature whistles varies with the individual.Footnote11
The dolphins appear to use whistles to maintain contact, when socializing and meeting other dolphin groups, and perhaps to coordinate school activities. For example, whistles are often heard when groups change direction or activity.
Woods Hole Oceanographic Institute Peter Tyack has teamed up with MIT electrical engineering professor David Staelin to develop software for a personal computer that could detect patterns and repetitive signals in the dolphin's squeaks and whistles.Footnote12 With such a tool researchers hope to learn about more about the dolphin whistles.
ECHOLOCATION
In addition to creating whistles, dolphins also create echolocation clicks. "Unlike lower-frequency, narrow band whistles, the dolphin's echolocation clicks, which it uses for navigation and for exploring features of its environment, are broad band pulses, ranging up to 150 kilohertz. Individual clicks last on the order of 70 milliseconds and are focused into beams through fatty tissues in the melon, or bulge, on the animal's forehead. Paul Nachtigall, director of research on biological sonar of cetaceans at the Naval Ocean Systems Center Laboratory in Kailua, Oahu, describes these beams as 'flashlights of sound.' Echoes from objects they impinge on are received and transmitted to the dolphin's brain through fatty deposits in the animal's lower jaw."Footnote13
"'Dolphins are much more flexible with echolocation that bats are,' says Nachtigall. Whereas bats' echolocation clicks tend to be frequency specific...dolphins can shift the peak frequency of the echolocation clicks 'all over the place.' They voluntarily control click amplitude as well. 'And their discrimination is amazing.'"Footnote14 "The dolphin seems to utilize low-frequency scans to get a coarse overall picture of the environment, and shifts to higher frequencies to examine things in more detail."Footnote15 Experiments at the Kailua laboratory have revealed that dolphins wearing soft latex eyecups can distinguish between two cylinders based on a wall thickness difference of just two tenths of a millimeter.
It has even been suggested that dolphins' echolocation clicks can penetrate solids in much the same way as our ultrasound devices, stunning fish and allowing the animals to peer inside one another. In addition, dolphins can determine direction stereophonically and distance and relative motion from the beat frequency caused by interference between the current and previous clicks.
Many researchers believe that dolphins can interpret some information from echolocation clicks of other dolphins. This idea has even been taken a step further, to a hypothesis where dolphins may communicate directly using their echolocation clicks. The dolphin constructs its image of the environment from the pair of acoustical waveforms arriving at its two acoustic receptors. The dolphin also has two separate sound producing organs which it can use together as well as independently. In humans the principal mode of communication is acoustic, different from the principal mode of perception, visual. Dolphins communicate using the same acoustic sense with which they perceive, and could possibly even be capable of transmitting imagery to another dolphin.
SOCIAL DOLPHINS
Observations of dolphins in the wild (and in captivity) indicate a high degree of social order in the dolphin societies. Females invest a full year in pregnancy, and at least three years in rearing each calf. Calves, leaving their mothers when they are three to six years old, join sub-adult groups of mixed sex. There they remain for about six years. After separating, males usually do not seek out or interact with their mothers often. In the sub-adult groups, close bonds develop between males that may last many years. As males age, they usually travel with only a few male associates or among bands of females. Although dolphins are promiscuous in their breeding habits, the matriarchal families are strong units in the dolphin society. When a female has her first baby, she often rejoins her mother's band and raises her calf in the company of females with calves of similar age. The birth of a new calf often results in visits by older siblings, both male and females, who have already separated from their mothers. Researchers have observed babysitting in the wild by older sisters, other mother band members, and once even a senior male. Dolphins have been observed forming playpens, U shaped formations of swimming mothers with the calves playing inside.
While very young, male calves shape their signature whistles to become like their mother's. Females modify theirs to become more distinct from their mothers. These differences could reflect the differences in the lives of the male and female dolphins in the dolphin society.Footnote16 Since females often rear their young in their mother's band, a distinct whistle would help her calf to distinguish mother from grandmother. Male signature whistles resembling their mother's may help prevent inbreeding.
CONCLUSION
Dolphins are among the most intelligent and socially complex animals. While we have not been able to determine exactly how extensively dolphins communicate among themselves, their level is at least quite good among mammals and the possibility exist that their communication goes well beyond what we have uncovered so far. Our efforts toward communication through an intermediate, artificial language have met with some success, but less than has been seen with primates. The better progress in bridging the gap with primates is probably due to the fact that we are actually very similar to the primate apes, whereas our bodies, environment, and perception differ greatly from the dolphins'. Indeed it is these differences that make the possibility of communication that much more intriguing.
'You'd think you were thinking: the intriguing questions surrounding the intelligence of the bottle-nosed dolphins. S. Witsch 'Mosaic 21:34-48 'Fall '90
'Interview: Louis Herman. J. Kaplan 'Omni 11:76-8+ 'Je '89
'Interview: Louis Herman. J. Kaplan 'Omni 11:76-8+ 'Je '89
'Conversations with the dolphins [work of L.M. Herman]. S. Chollar 'Psychology Today 23:52-6 'Ap '89
'Interview: Louis Herman. J. Kaplan 'Omni 11:76-8+ 'Je '89
'Interview: Louis Herman. J. Kaplan 'Omni 11:76-8+ 'Je '89
'Conversations with the dolphins [work of L.M. Herman]. S. Chollar 'Psychology Today 23:52-6 'Ap '89
'The Dolphin Report. S.H. Shane 'Sea Frontiers 37:36-55 'Mr/Ap '91
'If you need me, whistle. P. Tyack 'Natural History P60-1 'Ag '91
'If you need me, whistle. P. Tyack 'Natural History P60-1 'Ag '91
'The Dolphin Report. S.H. Shane 'Sea Frontiers 37:36-55 'Mr/Ap '91
'Dolphinspeak software. J. Parker 'Technology Review 94:14-15 'O '91
'Echolocation cognition, application. S. Wintsch 'Mosaic 21:47 'Fall '90
'Echolocation cognition, application. S. Wintsch 'Mosaic 21:47 'Fall '90
'Do Dolphins think without language? R. Strauch 'Sea Frontiers 30:111-14 'Mr/Ap '84
'If you need me, whistle. P. Tyack 'Natural History P60-1 'Ag '91
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