Dolphins Talking
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).
Bibliography
1. Brecht, M.
(1993). Communications: A Predictive Theory of Dolphin
Communication.
Kybernetes, 22, 39-53. 2. Erickson, D. (1993, March). Can Animals
Think?
Time, 146, 182-189. 3. Herman, L. M., Kuczaj II, S. A., & Holder,
M.
D. (1993). Responses to Anomalous Gestural Sequences by a
Language-Trained
Dolphin: Evidence for Processing of Semantic Relations
and Syntactic
Information. Journal of Experimental Psychology, 122,
184-194. 4. Herman, L. M.,
Morrel-Samuels, P., & Pack, A. (1990).
Bottlenosed Dolphin and Human
Recognition of Veridical and Degraded Video
Displays of an Artificial Gestural
Language. Journal of Experimental
Psychology, 119, 215-230. 5. Lilly, J. C.,
(1966). Lilly on Dolphins. Garden
City, N.Y.: Anchor Books. Anchor
Press/Doubleday. 6. McCowan, B., Hanser,
S. F., & Doyle, L.R. (1999).
Quantitative tools for comparing animal
communication systems: information
theory applied to bottlenose dolphin
whistle repertoires. Animal Behaviour, 57,
409-419. 7. Popov, V. V.,
& Supin, A. Y. (1991). Interaural intensity and
latency difference in the
dolphin¡¦s auditory system. Neuroscience Letters,
133, 295-297. 8.
Schusterman, R. J., Thomas, J. A., & Wood, F. G. (1986).
Dolphin
Cognition and Behavior: A Comparitive Approach. London: Lawrence
Erlbaum
Associates, Publishers. 9. Shane, S. H. (1991). Smarts.
Seafrontiers, 37, 40-43.
10. Supin, A. Y., Popov, V. V., & Klishin,
V. O. (1993). ABR Frequency
Tuning Curves in Dolphins. Journal of
Comparitive Psychology A, 173, 649-656.
11. Tyack, P. L.,& Sayigh, L.
S. (1989). These Dolphins Aren¡¦t Just
Whistling in the Dark. Oceanus,
32, 80-83.