Cetacean intelligence
Encyclopedia
Cetacean intelligence denotes the cognitive capabilities of the Cetacea
order of mammals, which includes whale
s, porpoise
s, and dolphin
s.
was previously considered an indicator of the intelligence of an animal. However, many other factors also affect intelligence. Recent discoveries concerning bird intelligence
have called into question the usefulness of brain size as an indicator. Since most of the brain is used for maintaining bodily functions, greater ratios of brain to body mass may increase the amount of brain mass available for more complex cognitive tasks. Allometric analysis indicates that mammalian brain size scales at approximately the 2/3 or 3/4 power of the body mass. Comparison of a particular animal's brain size with the expected brain size based on such allometric analysis provides an encephalization quotient
(EQ) that can be used as another indication of the animal's intelligence.
The discovery of spindle cells
(neurons without extensive branching, known also as "von Economo neurons", or VENs) in the brains of the humpback whale
, fin whale
, sperm whale
, killer whale, bottlenose dolphin
s, Risso’s dolphins, and beluga whales is another unique discovery. Humans, the great apes, and elephants are the only other species known to have spindle cells, species all well known for their high intelligence. Spindle neurons appear to play a central role in the development of intelligent behavior. Such a discovery may suggest a convergent evolution of these species. Harkeem et al's research on spindle neurons proposes the following theory:
brains also show a similar complexity to dolphin brains, and are also more convoluted than that of humans, and with a cortex "thicker than that of cetaceans". However, in dolphins, "no patterns of cellular distribution, nuclear subdivision, or cellular morphology indicate specialization of the LC
(coeruleus complex)" despite the large absolute brain size and unihemispheric sleep phenomenology of cetaceans. Moreover, it is generally agreed that the growth of the neocortex
, both absolutely and relative to the rest of the brain, during human evolution, has been responsible for the evolution of intelligence, however defined. While a complex neocortex usually indicates high intelligence, there are exceptions to this. For example, the spiny egg laying anteater (echidna
) has a highly developed brain, yet is not widely considered to be very intelligent.
Although many cetaceans have a great number of cortical neurons, after Homo sapiens, the species with the greatest number of cortical neurons and synapses is the elephant.
All sleeping mammals, including dolphins, experience a stage known as REM sleep. Unlike terrestrial
mammals, dolphin brains contain a paralimbic lobe, which may possibly be used for sensory processing. The dolphin is a voluntary breather, even during sleep, with the result that veterinary anaesthesia of dolphins is impossible, as it would result in asphyxiation. Ridgway reports that EEGs show alternating hemispheric asymmetry in slow waves during sleep, with occasional sleep-like waves from both hemispheres. This result has been interpreted to mean that dolphins sleep only one hemisphere of their brain at a time, possibly to control their voluntary respiration system or to be vigilant for predators. This is also given as explanation for the large size of their brains.
Dolphin brain stem
transmission time is faster than that normally found in humans, and is approximately equivalent to the speed found in rat
s. As echo-location is the dolphin's primary means of sensing its environment – analogous to eyes in primate
s – and since sound travels four and a half times faster in water than in air, scientists speculate that the faster brain stem transmission time, and perhaps the paralimbic lobe as well, assist speedy processing of sound. The dolphin's dependence on speedy sound processing is evident in the structure of its brain: its neural area devoted to visual imaging is only about one-tenth that of the human brain, while the area devoted to acoustical imaging is about 10 times that of the human brain. (This is unsurprising: primate
brains devote much more volume to visual processing than those of almost any other animal, and human brains more than other primates.) Sensory experiments suggest a great degree of cross-modal integration in the processing of shapes between echolocative and visual areas of the brain. Unlike the case of the human brain, the cetacean optic chiasm
is completely crossed, and there is behavioral evidence for hemispheric dominance for vision.
A recent research found that dolphins may be able to discriminate between numbers.
However, the same researcher suggested that "It may involve mimicry," he said, "as dolphins are unsurpassed in imitative abilities among nonhuman animals."
A commonly used definition of intelligence is "the ability to reason
, plan, solve problems, think abstractly, comprehend complex ideas, learn
quickly, and learn from experience
." This definition is separate from social/communicative traits or the ability to learn tricks (which can be done through conditioning), and because of this many people believe that dolphins are not as intelligent as humans.
Several researchers observing animals' ability to learn set formation tend to rank dolphins about the level of elephant
s in "intelligence" and show that dolphins do not have any unusual talent with problem solving compared with the other animals classed with very great intelligence. Macphail in his "Brain and intelligence in vertebrates" compared data from studies regarding learning "set formation" of animals. The result show that dolphins are skilled at performing this sort of standardized testing but not as adept as other animals in the study. The true extent of dolphin's intelligence is really unknown to humans in the sense that we, ourselves, have evolved over time to maintain sustenance on the land whereas they have evolved to live in the water.
s usually congregate in fairly small groups from 6 to 12 in number or, in some species, singly or in pairs. The individuals in these small groups know and recognise one another. Other species such as the oceanic Pantropical Spotted Dolphin
, Common Dolphin
and Spinner Dolphin
travel in large groups of hundreds of individuals. It is unknown whether every member of the group is acquainted with every other. However, there is no doubt that such large packs can act as a single cohesive unit - observations show that if an unexpected disturbance, such as a shark approach, occurs from the flank or from beneath the group, the group moves in near-unison to avoid the threat. This means that the dolphins must be aware not only of their near neighbors but also of other individuals nearby - in a similar manner to which humans perform "Audience wave
s". This is achieved by sight, and possibly also echolocation. One speculative hypothesis proposed by Jerison (1986) is that members of a pack of dolphins are able to share echolocation results with each other to create a better understanding of their surroundings.
Resident orca
s living in British Columbia, Canada, and Washington, United States live in extremely stable family groups. The basis of this social structure is the matriline, consisting of a mother and her offspring, who travel with her for life. Male orcas never leave their mothers' pods, while female offspring may branch off to form their own matriline if they have many offspring of their own. Males have a particularly strong bond with their mother, and travel with them their entire lives, which can exceed 50 years. It is interesting behavior, as it may seem that there would be no benefit from this except perhaps in hunting techniques, although they could join other groups to hunt. There are two interesting examples of this familial bond in males. Two male sons, identified as A38 and A39, constantly accompany their mother A30, despite the fact that she does not need protection and they can all hunt by themselves, and rarely leave her side. Researchers have noted that if one son wanders away, one always remains with the mother. Another example are the brothers A32, A37 and A46, whose mother (A36) died. Instead of the family disbanding, the three brothers remain constantly together.
Relationships in the orca population can be discovered through their vocalizations. Matrilines who share a common ancestor from only a few generations back share mostly the same dialect, comprising a pod. Pods who share some calls indicate a common ancestor from many generations back, and make up a clan. Interestingly, the orcas use these dialects to avoid in-breeding. They mate outside the clan, which is determined by the different vocalizations. On one occasion, an orca's mother and father were determined to be of the same clan, although in different pods. There is evidence that other species of dolphins may also have dialects.
In bottlenose dolphin
studies by Wells in Sarasota, Florida
, and Smolker in Shark Bay
, Australia
, females of a community are all linked either directly or through a mutual association in an overall social structure known as fission-fusion. Groups of the strongest association are known as "bands", and their composition can remain stable over years. There is some genetic evidence that band members may be related, but these bands are not necessarily limited to a single matrilineal line. There is no evidence that bands compete with each other. In the same research areas, as well as in Moray Firth
, Scotland
, males form strong associations of two to three individuals, with a coefficient of association between 70 and 100. These groups of males are known as "alliances", and members often display synchronous behaviors such as respiration, jumping, and breaching. Alliance composition is stable on the order of tens of years, and may provide a benefit for the acquisition of females for mating.
The complex social strategies of marine mammals such as bottlenose dolphins, "provide interesting parallels" with the social strategies of elephants and chimpanzees.
al air-core vortex
rings or "bubble ring
s". There are two main methods of bubble ring production: rapid puffing of a burst of air into the water and allowing it to rise to the surface, forming a ring; or swimming repeatedly in a circle and then stopping to inject air into the helical vortex currents thus formed. The dolphin will often then examine its creation visually and with sonar. They also appear to enjoy biting the vortex-rings they've created, so that they burst into many separate normal bubbles and then rise quickly to the surface. Certain whales are also known to produce bubble rings, or even bubble-nets for the purpose of foraging. Many dolphin species are also known for playing by riding in waves, whether natural waves near the shoreline in a method akin to human "body-surfing", or within the waves induced by the bow of a moving boat in a behavior known as bow-riding.
Dolphins have also been known to aid human swimmers in need.
s (Steno bredanensis), named Malia (a regular show performer at Sea Life Park) and Hou (a research subject at adjacent Oceanic Institute). The experiment tested when and whether the dolphins would identify that they were being rewarded (by fish) for originality in behavior and was very successful. However, since only two dolphins were involved in the experiment, the study is difficult to generalize.
Starting with the dolphin named Malia, the method of the experiment was to choose a particular behavior exhibited by her each day and reward each display of that behavior throughout the day's session. At the start of each new day Malia would present the prior day's behavior, but only when a new behavior was exhibited was a reward given. All behaviors exhibited were, at least for a time, known behaviors of dolphins. After approximately two weeks Malia apparently exhausted "normal" behaviors and began to repeat performances. This was not rewarded.
According to Pryor, the dolphin became almost despondent. However, at the sixteenth session without novel behavior, the researchers were presented with a flip they had never seen before. This was reinforced. As related by Pryor, after the new display: "instead of offering that again she offered a tail swipe we'd never seen; we reinforced that. She began offering us all kinds of behavior that we hadn't seen in such a mad flurry that finally we could hardly choose what to throw fish at..."
The second test subject, Hou, took thirty-three sessions to reach the same stage. On each occasion the experiment was stopped when the variability of dolphin behavior became too complex to make further positive reinforcement meaningful.
The same experiment was repeated with humans, and it took the volunteers about the same length of time to figure out what was being asked of them. After an initial period of frustration or anger, the humans realised they were being rewarded for novel behavior. In dolphins this realisation produced excitement and more and more novel behaviors - in humans it mostly just produced relief.
Captive orcas have often displayed interesting responses when they get 'bored' with activities. For instance, when Dr. Paul Spong
worked with the orca Skana, he researched her visual skills. However, after performing favorably in the 72 trials per day, Skana suddenly began consistently getting every answer wrong. Dr Spong concluded that a few fish were not enough motivation. He began playing music, which seemed to provide Skana with much more motivation.
At the Institute for Marine Mammal Studies in Mississippi, it has also been observed that the resident dolphins seem to show an awareness of the future. The dolphins are trained to keep their own tank clean by retrieving rubbish and bringing it to a keeper, to be rewarded with a fish. However, one dolphin, named Kelly, has apparently learned a way to get more fish, by hoarding the trash under a rock at the bottom of the pool and bringing it up one small piece at a time.
and wrapping them around their "bottle nose" to prevent abrasions.
Dolphins emit two distinct kinds of acoustic signals, which are called whistles and clicks.
There is strong evidence that some specific whistles, called signature whistles, are used by dolphins to identify and/or call each other; dolphins have been observed emitting both other specimens' signature whistles, and their own. A unique signature whistle develops quite early in a dolphin's life, and it appears to be created in an imitation of the signature whistle of the dolphin's mother.
Xitco reported the ability of dolphins to eavesdrop passively on the active echolocative inspection of an object by another dolphin. Herman
calls this effect the "acoustic flashlight" hypothesis, and may be related to findings by both Herman and Xitco on the comprehension of variations on the pointing gesture, including human pointing, dolphin postural pointing, and human gaze, in the sense of a redirection of another individual's attention
, an ability which may require theory of mind
.
The environment where dolphins live makes experiments much more expensive and complicated than for many other species; additionally, the fact that cetaceans can emit and hear sound
s (which are believed to be their main means of communication) in a range of frequencies much wider than that of humans means that sophisticated equipment, which was scarcely available in the past, is needed to record and analyse them. For example, clicks can contain significant energy in frequencies greater than 110 kHz (for comparison, it is unusual for a human to be able to hear sounds above 20 kHz), requiring that equipment have a sampling rates of at least 220 kHz; MHz-capable hardware is often used.
In addition to the acoustic communication channel, the visual modality
is also significant. The contrasting pigmentation of the body may be used, for example with "flashes" of the hypopigmented ventral area of some species, as can the production of bubble streams during signature whistling. Also, much of the synchronous and cooperative behaviors, as described in the Behavior section of this entry, as well as cooperative foraging methods, likely are managed at least partly by visual means.
While there is little evidence for dolphin language, experiments have shown that they can learn human sign language. Akeakamai
, a bottlenose dolphin, was able to understand both individual words and basic sentences like "touch the frisbee with your tail and then jump over it" (Herman, Richards, & Wolz 1984). Dolphins have also exhibited the ability to understand the significance of the ordering of each set of tasks in one sentence.
is seen, by some, to be a sign of highly-developed, abstract thinking. Self-awareness, though not well-defined scientifically, is believed to be the precursor to more advanced processes like meta-cognitive reasoning
(thinking about thinking) that are typical of humans. Scientific research in this field has suggested that bottlenose dolphin
s, alongside elephants and great apes
, possess self-awareness.
The most widely used test for self-awareness in animals is the mirror test
, developed by Gordon Gallup
in the 1970s, in which a temporary dye is placed on an animal's body, and the animal is then presented with a mirror.
Some scientists still disagree with these findings, arguing that the results of these tests are open to human interpretation and susceptible to the Clever Hans
effect. This test is much less definitive than when used for primates, because primates can touch the mark or the mirror, while dolphins cannot, making their alleged self-recognition behavior less certain. Critics argue that behaviors that are said to identify self-awareness resemble existing social behaviors, and so researchers could be misinterpreting social responses to another dolphin. The researchers counter-argue that the behaviors shown to evidence self-awareness are very different from normal responses to another dolphin, including paying significantly more attention to another dolphin than towards their mirror image. Dr. Gallup termed the results "the most suggestive evidence to date" of mirror self-recognition in dolphins, but "not definitive" because he was not certain that the dolphins were not interpreting the image in the mirror as another animal. Whereas apes can merely touch the mark on themselves with their fingers, dolphins show less definitive behavior of self-awareness, twisting and turning themselves to observe the mark.
As a further response to these criticisms, in 1995, Marten and Psarakos used television to test dolphin self-awareness. They showed dolphins real-time footage of themselves, recorded footage, and another dolphin. They concluded that their evidence suggested self-awareness rather than social behavior. However, this study has not been repeated since then, the results remain thus uncorroborated.
However, dolphins have since passed the mirror test. (Reiss, Marino)
Examples of cognitive abilities investigated in the dolphin include concept formation, sensory skills, and the use of mental representation of dolphins. Such research has been ongoing since the late 1970s, and includes the specific topics of: acoustic mimicry, behavioral mimicry (inter- and intra-specific), comprehension of novel sequences in an artificial language
(including non-finite state grammars as well as novel anomalous sequences), memory
, monitoring of self-behaviors (including reporting on these, as well as avoiding or repeating them), reporting on the presence and absence of objects, object categorization
, discrimination and matching (identity matching to sample, delayed matching to sample, arbitrary matching to sample, matching across echolocation
and vision, reporting that no identity match exists, etc.), synchronous creative behaviors between two animals, comprehension of symbols for various body parts, comprehension of the pointing gesture and gaze (as made by dolphins or humans), problem solving, echolocative eavesdropping, and more. Some researchers include Louis Herman
, Mark Xitco, John Gory, Stan Kuczaj, Adam Pack, and many others.
While these are largely laboratory studies, field studies relating to dolphin and cetacean cognition are also relevant to the issue of intelligence, including those proposing tool use, culture, fission-fusion social structure (including tracking alliances and other cooperative behavior), acoustic behavior (bottlenose dolphin signature whistles, sperm whale clicks, orca pod vocalizations), foraging methods (partial beaching
, cooperation with human fishermen, herding fish into a ball, etc.). See: Richard Connor, Hal Whitehead, Peter Tyack, Janet Mann, Randall Wells, Kenneth Norris, B. Wursig, John Ford, Louis Herman, Diana Reiss, Lori Marino, Sam Ridgway, Paul Nachtigall, Eduardo Mercado, Denise Herzing, Whitlow Au.
In contrast to the primates, cetaceans are particularly far-removed from humans in evolutionary time. Therefore, cognitive abilities generally cannot be claimed to derive from a common ancestor, whereas such claims are sometimes made by researchers studying primate cognition. Though cetaceans and humans (in common with all mammals) had a common ancestor in the distant past, it was almost certainly of distinctly inferior cognitive abilities compared to its modern descendants. The early divergence of the human—dolphin ancestry line creates a problem in what cognitive tasks to test for because human/dolphin brains have been naturally selected so differently, with completely different cognitive abilities favoring their very different environments. Therefore, an anthropomorphic problem exists with exactly what cognitive abilities to test, how to test them, as well as the validity of the experimental results because of the completely different evolutionary lineage and environment human and cetaceans have. It was for this reason Dr. John C. Lilly
proposed that developing a means of communicating with dolphins is necessary to have any future hope of communicating with an extra-terrestrial organism of equal-or-greater intelligence to man, which also would have evolved in a different environment and evolutionary lineage.
Popular media
Scientific or academic sources
Self-awareness research
Other or uncategorized
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
order of mammals, which includes whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s, porpoise
Porpoise
Porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen...
s, and dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s.
Brain size
Brain sizeBrain size
Brain size is one aspect of animal anatomy and evolution. Both overall brain size and the size of substructures have been analysed, and the question of links between size and functioning - particularly intelligence - has often proved controversial...
was previously considered an indicator of the intelligence of an animal. However, many other factors also affect intelligence. Recent discoveries concerning bird intelligence
Bird intelligence
Bird intelligence deals with the definition of intelligence and its measurement as it applies to birds. Traditionally, birds have been considered inferior in intelligence to mammals, and derogatory terms such as bird brains have been used colloquially in some cultures. Such perceptions are no...
have called into question the usefulness of brain size as an indicator. Since most of the brain is used for maintaining bodily functions, greater ratios of brain to body mass may increase the amount of brain mass available for more complex cognitive tasks. Allometric analysis indicates that mammalian brain size scales at approximately the 2/3 or 3/4 power of the body mass. Comparison of a particular animal's brain size with the expected brain size based on such allometric analysis provides an encephalization quotient
Encephalization quotient
Encephalization Quotient , or encephalization level is a measure of relative brain size defined as the ratio between actual brain mass and predicted brain mass for an animal of a given size, which is hypothesized to be a rough estimate of the intelligence of the animal.This is a more refined...
(EQ) that can be used as another indication of the animal's intelligence.
- Sperm whaleSperm WhaleThe sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter...
s (Physeter macrocephalus) have the largest brain mass of any extant animal, averaging 7.8 kg in mature males. - Bottlenose dolphinBottlenose DolphinBottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
s (Tursiops truncatus) have an absolute brain mass of 1500-1700 grams. This is slightly greater than that of humans (1300-1400 grams) and about four times that of chimpanzees (400 grams). - The brain to body mass ratioBrain to body mass ratioBrain-to-body mass ratio, also known as the brain to body weight ratio, is the ratio of brain weight to body weight, which is hypothesised to be a rough estimate of the intelligence of an animal. A more complex measurement, encephalization quotient, takes into account allometric effects of widely...
(as distinct from encephalization quotientEncephalization quotientEncephalization Quotient , or encephalization level is a measure of relative brain size defined as the ratio between actual brain mass and predicted brain mass for an animal of a given size, which is hypothesized to be a rough estimate of the intelligence of the animal.This is a more refined...
) in some members of the odontocete superfamily Delphinoidea (dolphins, porpoises, belugas, and narwhals) is second only to modern humans, and greater than all other mammals (there is debate whether that of the treeshrewTreeshrewThe treeshrews are small mammals native to the tropical forests of Southeast Asia. They make up the families Tupaiidae, the treeshrews, and Ptilocercidae, the pen-tailed treeshrews, and the entire order Scandentia. There are 20 species in 5 genera...
might be second) In some dolphins, it is less than half that of humans: 0.9% versus 2.1%. This comparison seems more favorable if the large amount of blubberBlubberBlubber is a thick layer of vascularized adipose tissue found under the skin of all cetaceans, pinnipeds and sirenians.-Description:Lipid-rich, collagen fiber–laced blubber comprises the hypodermis and covers the whole body, except for parts of the appendages, strongly attached to the musculature...
(15-20% of mass) that dolphins require for insulation is omitted. - The encephalization quotientEncephalization quotientEncephalization Quotient , or encephalization level is a measure of relative brain size defined as the ratio between actual brain mass and predicted brain mass for an animal of a given size, which is hypothesized to be a rough estimate of the intelligence of the animal.This is a more refined...
varies widely between species. The Orca/Killer whale has an EQ of 2.57, the franciscana dolphin of 1.67, the Ganges River dolphin of 1.55, the bottlenose dolphin of 4.14, and the tucuxi dolphin of 4.56. These are less than the human EQ of 7.44, but some are greater than that of chimpanzees at 2.49, dogs at 1.17, cats at 1.00, and mice at 0.50.
- One comparative way to try to gauge intelligenceIntelligenceIntelligence has been defined in different ways, including the abilities for abstract thought, understanding, communication, reasoning, learning, planning, emotional intelligence and problem solving....
is to compare a species’ brain size at birth to the completely developed adult brain. This indicates how much learning a species accumulates while young. The majority of mammals are born with a brain close to 90% of the adult weight. Humans are born with 28% of the adult weight, chimpanzeeChimpanzeeChimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
s with 54%, bottlenose dolphins with 42.5%, and elephants with 35%. By eighteen months, the brain mass of a bottlenose dolphin is about 80% of that of an adult. Human beings generally do not achieve this percentage until the age of three or four years .
The discovery of spindle cells
Spindle neuron
Spindle neurons, also called von Economo neurons , are a specific class of neurons that are characterized by a large spindle-shaped soma, gradually tapering into a single apical axon in one direction, with only a single dendrite facing opposite. Whereas other types of neurons tend to have many...
(neurons without extensive branching, known also as "von Economo neurons", or VENs) in the brains of the humpback whale
Humpback Whale
The humpback whale is a species of baleen whale. One of the larger rorqual species, adults range in length from and weigh approximately . The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal, often breaching and slapping the...
, fin whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...
, sperm whale
Sperm Whale
The sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter...
, killer whale, bottlenose dolphin
Bottlenose Dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
s, Risso’s dolphins, and beluga whales is another unique discovery. Humans, the great apes, and elephants are the only other species known to have spindle cells, species all well known for their high intelligence. Spindle neurons appear to play a central role in the development of intelligent behavior. Such a discovery may suggest a convergent evolution of these species. Harkeem et al's research on spindle neurons proposes the following theory:
There are a few mammals apart from hominids, cetaceans, and elephants that have brains somewhat larger than the apes. It would be interesting to determine whether or not these mammals, such as the giraffes and hippopotamuses, have VENs in parts of the brain corresponding to [frontoinsular] and [anterior cingulate cortex]. If they are present, it would suggest that the VEN morphology may be primarily related to absolute brain size. If not, it would suggest that the VENs may be related to behavioral specializations common to hominids, whales, and elephants.
Brain structure
ElephantElephant
Elephants are large land mammals in two extant genera of the family Elephantidae: Elephas and Loxodonta, with the third genus Mammuthus extinct...
brains also show a similar complexity to dolphin brains, and are also more convoluted than that of humans, and with a cortex "thicker than that of cetaceans". However, in dolphins, "no patterns of cellular distribution, nuclear subdivision, or cellular morphology indicate specialization of the LC
Locus ceruleus
The locus coeruleus , is a nucleus in the brainstem involved with physiological responses to stress and panic. It was discovered in the 18th century by Félix Vicq-d'Azyr....
(coeruleus complex)" despite the large absolute brain size and unihemispheric sleep phenomenology of cetaceans. Moreover, it is generally agreed that the growth of the neocortex
Neocortex
The neocortex , also called the neopallium and isocortex , is a part of the brain of mammals. It is the outer layer of the cerebral hemispheres, and made up of six layers, labelled I to VI...
, both absolutely and relative to the rest of the brain, during human evolution, has been responsible for the evolution of intelligence, however defined. While a complex neocortex usually indicates high intelligence, there are exceptions to this. For example, the spiny egg laying anteater (echidna
Echidna
Echidnas , also known as spiny anteaters, belong to the family Tachyglossidae in the monotreme order of egg-laying mammals. There are four extant species, which, together with the platypus, are the only surviving members of that order and are the only extant mammals that lay eggs...
) has a highly developed brain, yet is not widely considered to be very intelligent.
Although many cetaceans have a great number of cortical neurons, after Homo sapiens, the species with the greatest number of cortical neurons and synapses is the elephant.
All sleeping mammals, including dolphins, experience a stage known as REM sleep. Unlike terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
mammals, dolphin brains contain a paralimbic lobe, which may possibly be used for sensory processing. The dolphin is a voluntary breather, even during sleep, with the result that veterinary anaesthesia of dolphins is impossible, as it would result in asphyxiation. Ridgway reports that EEGs show alternating hemispheric asymmetry in slow waves during sleep, with occasional sleep-like waves from both hemispheres. This result has been interpreted to mean that dolphins sleep only one hemisphere of their brain at a time, possibly to control their voluntary respiration system or to be vigilant for predators. This is also given as explanation for the large size of their brains.
Dolphin brain stem
Brain stem
In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...
transmission time is faster than that normally found in humans, and is approximately equivalent to the speed found in rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s. As echo-location is the dolphin's primary means of sensing its environment – analogous to eyes in primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
s – and since sound travels four and a half times faster in water than in air, scientists speculate that the faster brain stem transmission time, and perhaps the paralimbic lobe as well, assist speedy processing of sound. The dolphin's dependence on speedy sound processing is evident in the structure of its brain: its neural area devoted to visual imaging is only about one-tenth that of the human brain, while the area devoted to acoustical imaging is about 10 times that of the human brain. (This is unsurprising: primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
brains devote much more volume to visual processing than those of almost any other animal, and human brains more than other primates.) Sensory experiments suggest a great degree of cross-modal integration in the processing of shapes between echolocative and visual areas of the brain. Unlike the case of the human brain, the cetacean optic chiasm
Optic chiasm
The optic chiasm or optic chiasma is the part of the brain where the optic nerves partially cross...
is completely crossed, and there is behavioral evidence for hemispheric dominance for vision.
Problem-solving ability
Some research shows that dolphins among other animals understand concepts such as numerical continuity (but not necessarily counting).A recent research found that dolphins may be able to discriminate between numbers.
However, the same researcher suggested that "It may involve mimicry," he said, "as dolphins are unsurpassed in imitative abilities among nonhuman animals."
A commonly used definition of intelligence is "the ability to reason
Reason
Reason is a term that refers to the capacity human beings have to make sense of things, to establish and verify facts, and to change or justify practices, institutions, and beliefs. It is closely associated with such characteristically human activities as philosophy, science, language, ...
, plan, solve problems, think abstractly, comprehend complex ideas, learn
LEARN
LEARN may refer to:* Law Enforcement Agency Resource Network, a website run by the Anti-Defamation League* LEARN diet, a brand name diet product...
quickly, and learn from experience
Experience
Experience as a general concept comprises knowledge of or skill in or observation of some thing or some event gained through involvement in or exposure to that thing or event....
." This definition is separate from social/communicative traits or the ability to learn tricks (which can be done through conditioning), and because of this many people believe that dolphins are not as intelligent as humans.
Several researchers observing animals' ability to learn set formation tend to rank dolphins about the level of elephant
Elephant
Elephants are large land mammals in two extant genera of the family Elephantidae: Elephas and Loxodonta, with the third genus Mammuthus extinct...
s in "intelligence" and show that dolphins do not have any unusual talent with problem solving compared with the other animals classed with very great intelligence. Macphail in his "Brain and intelligence in vertebrates" compared data from studies regarding learning "set formation" of animals. The result show that dolphins are skilled at performing this sort of standardized testing but not as adept as other animals in the study. The true extent of dolphin's intelligence is really unknown to humans in the sense that we, ourselves, have evolved over time to maintain sustenance on the land whereas they have evolved to live in the water.
Pod characteristics
Dolphin group sizes vary quite dramatically. River dolphinRiver dolphin
River dolphins are the four living species of dolphin that reside in freshwater rivers and estuaries. River dolphins inhabit areas of Asia and South America. They are classed in the Platanistoidea superfamily of cetaceans. Three species live in fresh water rivers. The fourth species, the La Plata...
s usually congregate in fairly small groups from 6 to 12 in number or, in some species, singly or in pairs. The individuals in these small groups know and recognise one another. Other species such as the oceanic Pantropical Spotted Dolphin
Pantropical Spotted Dolphin
The Pantropical Spotted Dolphin is a species of dolphin found in all the world's temperate and tropical oceans. The species was beginning to come under threat due to the killing of millions of individuals in tuna purse seines...
, Common Dolphin
Common dolphin
The common dolphin is the name given to two species of dolphin making up the genus Delphinus.Prior to the mid-1990s, most taxonomists only recognised one species in this genus, the common dolphin Delphinus delphis...
and Spinner Dolphin
Spinner Dolphin
The Spinner Dolphin is a small dolphin found in off-shore tropical waters around the world. It is famous for its acrobatic displays in which they spin longitudinally along their axis as they leap through the air.-Taxonomy:...
travel in large groups of hundreds of individuals. It is unknown whether every member of the group is acquainted with every other. However, there is no doubt that such large packs can act as a single cohesive unit - observations show that if an unexpected disturbance, such as a shark approach, occurs from the flank or from beneath the group, the group moves in near-unison to avoid the threat. This means that the dolphins must be aware not only of their near neighbors but also of other individuals nearby - in a similar manner to which humans perform "Audience wave
Audience wave
The wave or the Mexican wave is an example of metachronal rhythm achieved in a packed stadium when successive groups of spectators briefly stand and raise their arms...
s". This is achieved by sight, and possibly also echolocation. One speculative hypothesis proposed by Jerison (1986) is that members of a pack of dolphins are able to share echolocation results with each other to create a better understanding of their surroundings.
Resident orca
Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...
s living in British Columbia, Canada, and Washington, United States live in extremely stable family groups. The basis of this social structure is the matriline, consisting of a mother and her offspring, who travel with her for life. Male orcas never leave their mothers' pods, while female offspring may branch off to form their own matriline if they have many offspring of their own. Males have a particularly strong bond with their mother, and travel with them their entire lives, which can exceed 50 years. It is interesting behavior, as it may seem that there would be no benefit from this except perhaps in hunting techniques, although they could join other groups to hunt. There are two interesting examples of this familial bond in males. Two male sons, identified as A38 and A39, constantly accompany their mother A30, despite the fact that she does not need protection and they can all hunt by themselves, and rarely leave her side. Researchers have noted that if one son wanders away, one always remains with the mother. Another example are the brothers A32, A37 and A46, whose mother (A36) died. Instead of the family disbanding, the three brothers remain constantly together.
Relationships in the orca population can be discovered through their vocalizations. Matrilines who share a common ancestor from only a few generations back share mostly the same dialect, comprising a pod. Pods who share some calls indicate a common ancestor from many generations back, and make up a clan. Interestingly, the orcas use these dialects to avoid in-breeding. They mate outside the clan, which is determined by the different vocalizations. On one occasion, an orca's mother and father were determined to be of the same clan, although in different pods. There is evidence that other species of dolphins may also have dialects.
In bottlenose dolphin
Bottlenose Dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
studies by Wells in Sarasota, Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, and Smolker in Shark Bay
Shark Bay
Shark Bay is a World Heritage listed bay in Western Australia. The term may also refer to:* the locality of Shark Bay, now known as Denham* Shark Bay Marine Park* Shark Bay , a shark exhibit at Sea World, Gold Coast, Australia* Shire of Shark Bay...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, females of a community are all linked either directly or through a mutual association in an overall social structure known as fission-fusion. Groups of the strongest association are known as "bands", and their composition can remain stable over years. There is some genetic evidence that band members may be related, but these bands are not necessarily limited to a single matrilineal line. There is no evidence that bands compete with each other. In the same research areas, as well as in Moray Firth
Moray Firth
The Moray Firth is a roughly triangular inlet of the North Sea, north and east of Inverness, which is in the Highland council area of north of Scotland...
, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
, males form strong associations of two to three individuals, with a coefficient of association between 70 and 100. These groups of males are known as "alliances", and members often display synchronous behaviors such as respiration, jumping, and breaching. Alliance composition is stable on the order of tens of years, and may provide a benefit for the acquisition of females for mating.
The complex social strategies of marine mammals such as bottlenose dolphins, "provide interesting parallels" with the social strategies of elephants and chimpanzees.
Complex play
Dolphins are known to engage in complex play behavior, which includes such things as producing stable underwater toroidToroid
Toroid may refer to*Toroid , a doughnut-like solid whose surface is a torus.*Toroidal inductors and transformers which have wire windings on circular ring shaped magnetic cores.*Vortex ring, a toroidal flow in fluid mechanics....
al air-core vortex
Vortex
A vortex is a spinning, often turbulent,flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex...
rings or "bubble ring
Bubble ring
A bubble ring, or ring bubble, is an underwater ring vortex where an air bubble occupies the core of the vortex, forming a ring shape. The ring of air as well as the nearby water spins poloidally as it travels through the water, much like a flexible bracelet might spin when it is rolled on to a...
s". There are two main methods of bubble ring production: rapid puffing of a burst of air into the water and allowing it to rise to the surface, forming a ring; or swimming repeatedly in a circle and then stopping to inject air into the helical vortex currents thus formed. The dolphin will often then examine its creation visually and with sonar. They also appear to enjoy biting the vortex-rings they've created, so that they burst into many separate normal bubbles and then rise quickly to the surface. Certain whales are also known to produce bubble rings, or even bubble-nets for the purpose of foraging. Many dolphin species are also known for playing by riding in waves, whether natural waves near the shoreline in a method akin to human "body-surfing", or within the waves induced by the bow of a moving boat in a behavior known as bow-riding.
Cross-species cooperation
There have been instances in captivity of various species of dolphin and porpoise helping and interacting across species, including helping beached whales. Also they have been known to live alongside Resident (fish eating) Orca Whales for limited times.Dolphins have also been known to aid human swimmers in need.
Creative behavior
Aside from having exhibited the ability to learn complex tricks, dolphins have also demonstrated the ability to produce creative responses. This was studied by Karen Pryor during the mid-1960s at Sea Life Park in Hawaii, and was published as "The Creative Porpoise: Training for Novel Behavior" in 1969. The two test subjects were two rough-toothed dolphinRough-toothed Dolphin
The Rough-toothed dolphin is species of dolphin that can be found in deep warm and tropical waters around the world.The species was first described by Georges Cuvier in 1823...
s (Steno bredanensis), named Malia (a regular show performer at Sea Life Park) and Hou (a research subject at adjacent Oceanic Institute). The experiment tested when and whether the dolphins would identify that they were being rewarded (by fish) for originality in behavior and was very successful. However, since only two dolphins were involved in the experiment, the study is difficult to generalize.
Starting with the dolphin named Malia, the method of the experiment was to choose a particular behavior exhibited by her each day and reward each display of that behavior throughout the day's session. At the start of each new day Malia would present the prior day's behavior, but only when a new behavior was exhibited was a reward given. All behaviors exhibited were, at least for a time, known behaviors of dolphins. After approximately two weeks Malia apparently exhausted "normal" behaviors and began to repeat performances. This was not rewarded.
According to Pryor, the dolphin became almost despondent. However, at the sixteenth session without novel behavior, the researchers were presented with a flip they had never seen before. This was reinforced. As related by Pryor, after the new display: "instead of offering that again she offered a tail swipe we'd never seen; we reinforced that. She began offering us all kinds of behavior that we hadn't seen in such a mad flurry that finally we could hardly choose what to throw fish at..."
The second test subject, Hou, took thirty-three sessions to reach the same stage. On each occasion the experiment was stopped when the variability of dolphin behavior became too complex to make further positive reinforcement meaningful.
The same experiment was repeated with humans, and it took the volunteers about the same length of time to figure out what was being asked of them. After an initial period of frustration or anger, the humans realised they were being rewarded for novel behavior. In dolphins this realisation produced excitement and more and more novel behaviors - in humans it mostly just produced relief.
Captive orcas have often displayed interesting responses when they get 'bored' with activities. For instance, when Dr. Paul Spong
Paul Spong
Dr. Paul Spong is a neuroscientist and cetologist from New Zealand. He has spent more than 30 years researching orcas in British Columbia, and is credited with increasing public awareness of whaling, through his involvement with Greenpeace....
worked with the orca Skana, he researched her visual skills. However, after performing favorably in the 72 trials per day, Skana suddenly began consistently getting every answer wrong. Dr Spong concluded that a few fish were not enough motivation. He began playing music, which seemed to provide Skana with much more motivation.
At the Institute for Marine Mammal Studies in Mississippi, it has also been observed that the resident dolphins seem to show an awareness of the future. The dolphins are trained to keep their own tank clean by retrieving rubbish and bringing it to a keeper, to be rewarded with a fish. However, one dolphin, named Kelly, has apparently learned a way to get more fish, by hoarding the trash under a rock at the bottom of the pool and bringing it up one small piece at a time.
Use of tools
, scientists have observed limited groups of bottlenose dolphins around the Australian Pacific using a basic tool. When searching for food on the sea floor, many of these dolphins were seen tearing off pieces of spongeSea sponge
Sponges are animals of the phylum Porifera . Their bodies consist of jelly-like mesohyl sandwiched between two thin layers of cells. While all animals have unspecialized cells that can transform into specialized cells, sponges are unique in having some specialized cells, but can also have...
and wrapping them around their "bottle nose" to prevent abrasions.
Communication
Whale song is the sounds made by whales and which is used for different kinds of communication.Dolphins emit two distinct kinds of acoustic signals, which are called whistles and clicks.
- Clicks - quick broadband burst pulses - are used for echolocationAnimal echolocationEcholocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
, although some lower-frequency broadband vocalizations may serve a non-echolocative purpose such as communication; for example, the pulsed calls of Orcas. Pulses in a click train are emitted at intervals of ~35-50 millisecondMillisecondA millisecond is a thousandth of a second.10 milliseconds are called a centisecond....
s, and in general these inter-click intervals are slightly greater than the round-trip time of sound to the target. - Whistles - narrow-band frequency modulated (FM)Frequency modulationIn telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
signals - are used for communicative purposes, such as contact calls, the pod-specific dialects of resident OrcaOrcaThe killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...
s, or the signature whistle of bottlenose dolphinBottlenose DolphinBottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
s.
There is strong evidence that some specific whistles, called signature whistles, are used by dolphins to identify and/or call each other; dolphins have been observed emitting both other specimens' signature whistles, and their own. A unique signature whistle develops quite early in a dolphin's life, and it appears to be created in an imitation of the signature whistle of the dolphin's mother.
Xitco reported the ability of dolphins to eavesdrop passively on the active echolocative inspection of an object by another dolphin. Herman
Louis Herman
Louis Herman is a researcher of dolphin sensory abilities, dolphin cognition, and humpback whales. He is currently professor in the Department of Psychology and a cooperating faculty member of the Department of Oceanography at the University of Hawaii at Manoa...
calls this effect the "acoustic flashlight" hypothesis, and may be related to findings by both Herman and Xitco on the comprehension of variations on the pointing gesture, including human pointing, dolphin postural pointing, and human gaze, in the sense of a redirection of another individual's attention
Attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....
, an ability which may require theory of mind
Theory of mind
Theory of mind is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others and to understand that others have beliefs, desires and intentions that are different from one's own...
.
The environment where dolphins live makes experiments much more expensive and complicated than for many other species; additionally, the fact that cetaceans can emit and hear sound
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
s (which are believed to be their main means of communication) in a range of frequencies much wider than that of humans means that sophisticated equipment, which was scarcely available in the past, is needed to record and analyse them. For example, clicks can contain significant energy in frequencies greater than 110 kHz (for comparison, it is unusual for a human to be able to hear sounds above 20 kHz), requiring that equipment have a sampling rates of at least 220 kHz; MHz-capable hardware is often used.
In addition to the acoustic communication channel, the visual modality
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
is also significant. The contrasting pigmentation of the body may be used, for example with "flashes" of the hypopigmented ventral area of some species, as can the production of bubble streams during signature whistling. Also, much of the synchronous and cooperative behaviors, as described in the Behavior section of this entry, as well as cooperative foraging methods, likely are managed at least partly by visual means.
While there is little evidence for dolphin language, experiments have shown that they can learn human sign language. Akeakamai
Akeakamai
Akeakamai was a female Atlantic bottlenose dolphin, who along with a companion female dolphin named Phoenix, as well as tankmates Elele and Hiapo, were the subjects of Louis Herman's animal language studies at the Kewalo Basin Marine Mammal Laboratory in Honolulu, Hawaii...
, a bottlenose dolphin, was able to understand both individual words and basic sentences like "touch the frisbee with your tail and then jump over it" (Herman, Richards, & Wolz 1984). Dolphins have also exhibited the ability to understand the significance of the ordering of each set of tasks in one sentence.
Self-awareness
Self-awarenessSelf-awareness
Self-awareness is the capacity for introspection and the ability to reconcile oneself as an individual separate from the environment and other individuals...
is seen, by some, to be a sign of highly-developed, abstract thinking. Self-awareness, though not well-defined scientifically, is believed to be the precursor to more advanced processes like meta-cognitive reasoning
Metacognition
Metacognition is defined as "cognition about cognition", or "knowing about knowing." It can take many forms; it includes knowledge about when and how to use particular strategies for learning or for problem solving...
(thinking about thinking) that are typical of humans. Scientific research in this field has suggested that bottlenose dolphin
Bottlenose Dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
s, alongside elephants and great apes
Great Apes
Great Apes may refer to*Great apes, species in the biological family Hominidae, including humans, chimpanzees, gorillas, and orangutans*Great Apes , a 1997 novel by Will Self...
, possess self-awareness.
The most widely used test for self-awareness in animals is the mirror test
Mirror test
The mirror test is a measure of self-awareness, as animals either possess or lack the ability to recognize themselves in a mirror.The test was developed by Gordon Gallup Jr. in 1970, based in part on observations made by Charles Darwin. While visiting a zoo, Darwin held a mirror up to an orangutan...
, developed by Gordon Gallup
Gordon G. Gallup
Gordon G. Gallup, Jr. is a psychologist of the University at Albany's Psychology department, researching biopsychology. He received his Ph.D. from Washington State University in 1968, after which he joined the faculty of the Psychology Department at Tulane University...
in the 1970s, in which a temporary dye is placed on an animal's body, and the animal is then presented with a mirror.
Some scientists still disagree with these findings, arguing that the results of these tests are open to human interpretation and susceptible to the Clever Hans
Clever Hans
Clever Hans was an Orlov Trotter horse that was claimed to have been able to perform arithmetic and other intellectual tasks....
effect. This test is much less definitive than when used for primates, because primates can touch the mark or the mirror, while dolphins cannot, making their alleged self-recognition behavior less certain. Critics argue that behaviors that are said to identify self-awareness resemble existing social behaviors, and so researchers could be misinterpreting social responses to another dolphin. The researchers counter-argue that the behaviors shown to evidence self-awareness are very different from normal responses to another dolphin, including paying significantly more attention to another dolphin than towards their mirror image. Dr. Gallup termed the results "the most suggestive evidence to date" of mirror self-recognition in dolphins, but "not definitive" because he was not certain that the dolphins were not interpreting the image in the mirror as another animal. Whereas apes can merely touch the mark on themselves with their fingers, dolphins show less definitive behavior of self-awareness, twisting and turning themselves to observe the mark.
As a further response to these criticisms, in 1995, Marten and Psarakos used television to test dolphin self-awareness. They showed dolphins real-time footage of themselves, recorded footage, and another dolphin. They concluded that their evidence suggested self-awareness rather than social behavior. However, this study has not been repeated since then, the results remain thus uncorroborated.
However, dolphins have since passed the mirror test. (Reiss, Marino)
Comparative cognition
Research of the comparative cognition of the dolphin is one of the primary methods of the investigation of cetacean intelligence.Examples of cognitive abilities investigated in the dolphin include concept formation, sensory skills, and the use of mental representation of dolphins. Such research has been ongoing since the late 1970s, and includes the specific topics of: acoustic mimicry, behavioral mimicry (inter- and intra-specific), comprehension of novel sequences in an artificial language
Animal language
Animal language is the modeling of human language in non human animal systems. While the term is widely used, researchers agree that animal languages are not as complex or expressive as human language....
(including non-finite state grammars as well as novel anomalous sequences), memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....
, monitoring of self-behaviors (including reporting on these, as well as avoiding or repeating them), reporting on the presence and absence of objects, object categorization
Categorization
Categorization is the process in which ideas and objects are recognized, differentiated and understood. Categorization implies that objects are grouped into categories, usually for some specific purpose. Ideally, a category illuminates a relationship between the subjects and objects of knowledge...
, discrimination and matching (identity matching to sample, delayed matching to sample, arbitrary matching to sample, matching across echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
and vision, reporting that no identity match exists, etc.), synchronous creative behaviors between two animals, comprehension of symbols for various body parts, comprehension of the pointing gesture and gaze (as made by dolphins or humans), problem solving, echolocative eavesdropping, and more. Some researchers include Louis Herman
Louis Herman
Louis Herman is a researcher of dolphin sensory abilities, dolphin cognition, and humpback whales. He is currently professor in the Department of Psychology and a cooperating faculty member of the Department of Oceanography at the University of Hawaii at Manoa...
, Mark Xitco, John Gory, Stan Kuczaj, Adam Pack, and many others.
While these are largely laboratory studies, field studies relating to dolphin and cetacean cognition are also relevant to the issue of intelligence, including those proposing tool use, culture, fission-fusion social structure (including tracking alliances and other cooperative behavior), acoustic behavior (bottlenose dolphin signature whistles, sperm whale clicks, orca pod vocalizations), foraging methods (partial beaching
Beached whale
A beached whale is a whale that has stranded itself on land, usually on a beach. Beached whales often die due to dehydration, the body collapsing under its own weight, or drowning when high tide covers the blowhole.-Species:...
, cooperation with human fishermen, herding fish into a ball, etc.). See: Richard Connor, Hal Whitehead, Peter Tyack, Janet Mann, Randall Wells, Kenneth Norris, B. Wursig, John Ford, Louis Herman, Diana Reiss, Lori Marino, Sam Ridgway, Paul Nachtigall, Eduardo Mercado, Denise Herzing, Whitlow Au.
In contrast to the primates, cetaceans are particularly far-removed from humans in evolutionary time. Therefore, cognitive abilities generally cannot be claimed to derive from a common ancestor, whereas such claims are sometimes made by researchers studying primate cognition. Though cetaceans and humans (in common with all mammals) had a common ancestor in the distant past, it was almost certainly of distinctly inferior cognitive abilities compared to its modern descendants. The early divergence of the human—dolphin ancestry line creates a problem in what cognitive tasks to test for because human/dolphin brains have been naturally selected so differently, with completely different cognitive abilities favoring their very different environments. Therefore, an anthropomorphic problem exists with exactly what cognitive abilities to test, how to test them, as well as the validity of the experimental results because of the completely different evolutionary lineage and environment human and cetaceans have. It was for this reason Dr. John C. Lilly
John C. Lilly
John Cunningham Lilly was an American physician, neuroscientist, psychoanalyst, psychonaut, philosopher and writer....
proposed that developing a means of communicating with dolphins is necessary to have any future hope of communicating with an extra-terrestrial organism of equal-or-greater intelligence to man, which also would have evolved in a different environment and evolutionary lineage.
See also
- Animal cognitionAnimal cognitionAnimal cognition is the title given to the study of the mental capacities of non-human animals. It has developed out of comparative psychology, but has also been strongly influenced by the approach of ethology, behavioral ecology, and evolutionary psychology...
- Morgan's CanonMorgan's CanonCoined by 19th-century British psychologist C. Lloyd Morgan, Morgan's Canon remains a fundamental precept of comparative psychology...
- John C. LillyJohn C. LillyJohn Cunningham Lilly was an American physician, neuroscientist, psychoanalyst, psychonaut, philosopher and writer....
- Pioneer researcher in human/dolphin communication. - Louis HermanLouis HermanLouis Herman is a researcher of dolphin sensory abilities, dolphin cognition, and humpback whales. He is currently professor in the Department of Psychology and a cooperating faculty member of the Department of Oceanography at the University of Hawaii at Manoa...
- Scientist in dolphin cognition and sensory abilities - Animal LanguageAnimal languageAnimal language is the modeling of human language in non human animal systems. While the term is widely used, researchers agree that animal languages are not as complex or expressive as human language....
- Vocal learningVocal learningVocal learning is the ability of animals to modify vocal signals in form as a result of experience with those of other individuals. This can lead to signals that are either similar or dissimilar to the model...
- Spindle neuronSpindle neuronSpindle neurons, also called von Economo neurons , are a specific class of neurons that are characterized by a large spindle-shaped soma, gradually tapering into a single apical axon in one direction, with only a single dendrite facing opposite. Whereas other types of neurons tend to have many...
- Military dolphinMilitary dolphinA military dolphin is a dolphin trained for military uses. The United States and Russian militaries have trained and employed oceanic dolphins for several reasons. Such military dolphins have been trained to rescue lost naval swimmers or to locate underwater mines.The U.S. Navy trains dolphins and...
- U.S. Navy Marine Mammal ProgramU.S. Navy Marine Mammal ProgramThe U.S. Navy Marine Mammal Program is a program administered by the U.S. Navy which studies the military use of marine mammals—principally Bottlenose Dolphins and California Sea Lions—and trains animals to perform tasks such as ship and harbor protection, mine detection and clearance, and...
External links
Cetacean brainPopular media
Scientific or academic sources
Self-awareness research
Other or uncategorized