Dolphins Essay, Research Paper
Bottlenose dolphins are among the most vocal of the nonhuman animals and
exhibit remarkable development of the sound production and auditory
mechanisms. This can be seen in audition, which is shown in the animal?s
highly refined echolocation ability, and in tightly organized schools in which
they live that are made up by sound communication. In testing the
communication skills of dolphins, extensive studies have been done on vocal
mimicry, in which the animal imitates computer-generated sounds in order to
test motor control in terms of cognitive ability. Language comprehension on
the other hand has been tested through labeling of objects, which has proven
to be successful regarding the association of sound and object stimulus. The
biggest question in dolphin communication, is whether or not the species is
capable of intentional communicative acts. Though results from studies have
been debatable, the key to understanding the extent to this ?language? is to
determine whether they have a repertoire of grammatical rules that generate
organized sequences. In determining this, the greatest accomplishment for
both the scientist and all of humanity, would be to accomplish interspecies
communication, creating a bridge between humans and animals which could
open up a new understanding of the unknown world of wildlife. Most
importantly, it is necessary to understand the incredible aptitude of dolphin
communicative skills, and the impressive intelligence the animal possesses
which allows for a great deal of intraspecies and interspecies communication
(Schusterman, Thomas, & Wood, 1986). The acoustical reception and
processing abilities of the bottlenosed dolphins have generally been shown to
be among the most sophisticated of any animal so far examined (Popper,
1980 as cited by Schusterman et al. 1986). In order to understand the
complexity of these highly mechanized acoustic systems, it is necessary to
learn the process for which the dolphin hears. In most water-adapted
cetaceans, tissue conduction is the primary route of sound conduction to the
middle ear. The isolation of the bullae shows an adaptation for tissue
conducted sound. The lower jaw contains fat that is closely associated with
the impedance of seawater. The lower jawbone of most odontocetes
becomes broadened and quite thin posteriorly, and the fat forms an oval
shape that closely corresponds to the area of minimum thickness of the jaw.
This fat body leads directly to the bulla, producing a sound path to the ear
structures located deep within the head. Paired and single air sacs are
scattered throughout the skull, which serve to channel these tissue-conducted
sounds (Popov & Supin, 1991). Other than this description, there are still
more studies needed to determine the function of the middle ear and the type
of bone conduction that occurs within the bulla. Due to detailed audiograms,
dolphins have been shown to have the ability to detect high-frequency
sounds. In an experiment by Johnson (1966) as cited in Schusterman et al.
(1986), sine-wave sounds ranging in frequency from 75 Hz to 150 Hz were
presented to a bottle-nosed dolphin. The animal was trained to swim in a
stationary area within a stall and to watch for a light to come on. Following
the light presentation a sound was sometimes presented. If the dolphin heard
the sound, its task was to leave the area and push a lever. Sound intensity
levels were varied by a staircase method of 1, 2, or 3 dB steps. The resulting
audiogram, compared to the human aerial audiogram, showed that at regions
of best sensitivity for each, thresholds for human and dolphin are quite similar,
but separated by about 50 kHz in frequency, showing that the animal?s inner
ear function is very similar to a human. The experiments done on dolphin
auditory functions have generally shown a finely adapted sound reception
system. This would be expected due to the highly adapted echolocation
ability of the bottlenosed dolphin and other cetaceans. Results of work on
absolute thresholds, critical bandwidths, frequency discrimination, and sound
localization all indicate that the dolphin auditory system is at least as good or
better than the human system. This is in spite of the fact that sound travels five
times as fast under water as it does in air (Popov et al. 1991). The
bottlenosed dolphin in captivity produces two categories of vocalizations: (a)
narrow-band, frequency-varying, continuous tonal sounds referred to as
?whistles? and (b) broad-band pulsed sounds expressed as trains of very
short duration clicks of varying rates (Evans, 1967, as cited in Schusterman
et al. 1986). The pulsed sounds are used for both communication and
echolocation, and the whistles are found to be used primarily for
communication (Herman & Tavolga, 1980, as cited in Schusterman et al.
1986). Descriptions in literature emphasizing either the whistles or the pulsed
sounds have led to contradictory hypotheses concerning the communication
system of the dolphin. It has been reported that individually specific whistles
often make up over 90% of the whistle repertoire of captive bottlenosed
dolphins (Popov et al. 1991). A number of observations of apparent vocal
mimicry have been made, though with no systematic investigation of the
degree of vocal flexibility. The observed variability in the whistles, combined
with the difficulty of identifying individual vocalizing dolphins in a group, has
led to speculation that the whistles might be a complex, shared system, in
which specific meanings could be assigned to specific whistles. Consideration
of vocal mimicry has been taken to understand its relation to cognitive
complexity, and to the potential use of vocal response for communication in
an artificial language. In one study done by McCowan, Hanser, & Doyle,
(1999), the dolphin was able to learn to mimic a number of
computer-generated model sounds with high fidelity and reliability. The
dolphin using its whistle mode of vocalization imitated all of the sounds, and
all were distinct from the unreinforced whistles produced prior to training.
The large majority of each dolphin?s whistle vocalizations were individually
specific acoustic patterns, described as a ?signature whistle?; the rest of the
whistles were short chirps. The results of the mimicry training have shown that
dolphins can mimic tonal sounds with frequencies between 4 and 20 Hz. Due
to this research, scientists can now learn from these mimicry skills how to
understand and develop natural communication based on a stronger emphasis
on the animal?s cognitive abilities (Brecht, 1993). In object labeling, the
dolphins seemed to understand the task of associating model sounds with
displayed objects. Progress was most rapid when the model sound was
always presented at full intensity, but the probability of its being presented on
any given trial was systematically decreased over successive trials. There
wasn?t any confusion of the objects themselves, but only a tendency to drift in
the quality of the rendition of the labels. This demonstration of symbolic use
of vocalizations could lead to the investigation of the potential of animals to
form referential concepts, thus creating a new understanding of dolphin
communication and its uses in the wild. The main purpose of study in dolphin
language, is the interest in whether the animal?s speech is intentional
communication like our own human speech. The fact that awareness as
applied to the phenomena of human communication also implies something
we would not attribute to animals-and this is the awareness that
communicative acts are behaviors about behaviors (Crook, 1983, as cited in
Schusterman et al. 1986). Language, as we know it, could not exist without
the capacity for intentional communication, as all linguistic communications
are, by definition, intentional. Dolphins have been observed to have some of
these intentional communication characteristics, as their behaviors have
shown in captivity. For example, dolphins have been observed to squirt or
splash water at strangers who come near their tank. After squirting the water
the dolphin will raise itself out of the water to curiously observe what effect
their behavior had on the stranger. Although this behavior is not communitive,
nonetheless, it seems to suggest that the dolphin is aware of the effect of its
behavior on others, showing that it has the cognitive ability for intentional
communication (Erickson, 1993). Communication between humans and
dolphins occurs mostly through a gestural language that borrows some words
from American Sign Language. The trainers make the gestures with big arm
movements, asking the animal to follow commands such as ?person left
Frisbee fetch,? which means ?bring the Frisbee on the left to the person in the
pool?. In one study, two bottlenosed dolphins were tested in proficiency in
interpreting gestural language signs and compared against humans who
viewed the same videos of veridical and degraded gestures. The dolphins
were found to recognize gestures as accurately as fluent humans, and the
results suggested that the dolphins had constructed an interconnected
network of semantic and gestural representations in their memory (Herman,
Morrel-Samuels, & Pack, 1990). Such requests probe the dolphins
understanding of word order and test the animal?s grammatical competence.
It has also been determined that dolphins can form a generalized concept
about an object: they respond correctly to commands involving a hoop, no
matter whether the hoop is round, octagonal, or square. The animals seem to
have a conceptual grasp of the words they learn, showing an understanding of
the core attributes of human language, those being semantics and syntax
(Erickson, 1993). Though this information seems compelling for dolphin
language abilities, to determine whether or not they are capable of complex
intentional communications, researchers must continue to investigate their
receptive capacities, and to attempt to provide them with a communication
system that would tap their productive capacities. Is interspecies
communication possible? Could we someday be having philosophical
discussions with a bottlenosed dolphin? Though these questions seem
ridiculous, there was much debate over these questions when a medical
doctor named John Lilly came out with hopeful findings of dolphin intelligence
in the 1960s (Shane, 1991). In the first true research of dolphin
communication and intelligence, Lilly set out to show that through the
correlation of brain size and IQ, the bottlenose dolphin was perhaps smarter
than humans and began a growing interest in dolphins and their language
through whistles. Though dolphins are exceedingly intelligent creatures, no
real scientific evidence has yet been found to totally support the many
conceptions about the animal?s intelligence. Lilly (1966) states, ?A dolphin . .
. naturally uses other sounds to convey and receive ?meaning?: creaking for
night-time and murky-water finding and recognition, putt-putting and whistles
for exchanges with other dolphins, and even air wailing to excite human
responses in the way of fish or applause. If a dolphin is copying our speech,
he?ll copy that part of what he hears which in his ?language? conveys
meanings.? Although this excerpt shows an incredible capability for dolphins
to produce intelligent communication, it is findings such as these, which lack
scientific support and have lost credibility among other dolphin researchers in
the past few decades. Though his findings lack support, Lilly was important in
bringing forth interest among people and therefore funds towards more
scientifically based research and experiments that have helped us learn more
about communication skills and intelligence of dolphins (Tyack et al. 1989).
In order to clearly understand if dolphins are creating intentional, intelligent
communicative sounds and meanings, it is necessary to break down the vocal
signals into repertoires and analyze those individually. The breaking down of
dolphin signaling into component units has just now begun and the task will be
to discover if, when, and to what extent they structure formalized sequences
of signal units. To determine whether they have a repertoire of grammatical
rules that generates organized sequences will be difficult, and it will be
necessary to obtain extended and continuous recordings. Patterns must be
found and compared to other dolphin recordings in order to obtain the most
accurate and universal findings for language among bottlenose dolphins
(Herman, Kuczjac II, & Holder, 1993). Through many more years of careful
study of these sounds, it is hopeful that our scientists can determine capacities
and meanings behind dolphin language. Though interspecies communication
seems unlikely at this point in time, through new studies being conducted our
conception of dolphins as communicative animals seems more possible.
Intentional communication through gestural understanding is the best finding
so far in the study of these intelligent animals, and leads many to believe there
is a lot more to dolphin?s communication skills than has yet been uncovered.
In tests done in mimicry and labeling of objects, it seems that the capacity the
bottlenose dolphin has for learning and understanding is large enough to make
taught communication a realistic goal in the future of dolphin training. The
highly specialized auditory and vocal mechanisms of the animal have helped
lead the way to a better understanding of cetacean ear anatomy and sound
production mechanisms, and these functions can now be seen as complex
structures unlike any found above water. Though more research needs to be
done before any true conclusions can be made about dolphin language, from
what we do know the bottlenose dolphin is among the most vocal of
nonhuman animals and exhibits remarkable development of sound production
and auditory mechanisms (Schusterman et al. 1986).
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