Language Learning
Louis M. Herman
Kewalo Basin Marine Mammal Laboratory, University of Hawaii
and The Dolphin Institute, Honolulu, Hawaii
Human language and ape language
No single trait has been linked more closely with the human species
than has language. However, the definition of language and its uniqueness
as a human trait continue to be areas of study and debate. Some,
such as the linguist Noam Chomsky, take an evolutionary discontinuity
position professing that language is a highly nunique adaptation
supported by special modifications of the brain that appear only
in humans. Others, such as the anthropologist Barbara King, favor
a continuity position, which suggests that language must have its
roots in earlier hominoid adaptations for
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communication, and that some of these adaptations may still be extant
in modern ape species. The work on teaching various language-like
systems to apes by Beatrice and Alan Gardner, David Premack, Duane
Rumbaugh and others, beginning in the mid-1960s and continuing throughout
the decade of the 70s, seemed to provide a genuine link between human
and ape in fundamental language competency. This early work reported
that chimpanzees were able to learn to use and understand not only
words but also sentences. Sentences give human language its great
communicative power, through the infinite variety of meanings that
can be constructed by the recombination of words. To understand a
sentence the human listener must take account of both the meaning
of the words and their grammatical relationships to one another, as
governed by word order or other syntactic devices. This early work
on teaching language to apes was thrown into disarray, however, by
additional studies and criticisms from other researchers, such as
Herbert Terrace and Carolyn Ristau. These researchers argued that
the putative “sentences” produced by the apes were largely
an artifact of context, imitation, or cueing. In particular, although
sequences of words were indeed produced by the apes, the sequences
had no syntactic structure that enhanced, explained, or modified meaning.
Until recently, the work with apes was focused on language production
and paid scant attention to language comprehension. Investigators
attempted to teach the apes to produce language—where words
were represented by gestures, keyboard symbols, or other types of
artificial symbols. These investigators assumed that if the ape
produced a word, or a series of words, that it therefore understood
what the word or sequence represented. They also assumed that the
ape could understand those same words or sequences when produced
by the human partner. These assumptions, when finally tested, proved
false. It was shown, instead, that comprehension did not automatically
flow from language production. The preeminence of comprehension
in language development, only recently appreciated in the ape language
field, has long been emphasized among those studying child language.
Language comprehension by young children develops earlier than language
production, and even into adulthood comprehension vocabularies exceed
speaking vocabularies.
Recent work with bonobo chimpanzees, pioneered by Sue Savage-Rumbaugh,
has emphasized language comprehension and has progressed well beyond
the earlier ape language studies. The bonobos have shown an ability
to learn to understand instructions given in spoken English sentences.
Together with some of her earlier work, Savage-Rumbaugh has shown
that chimpanzees can learn to appreciate the symbols (words) of
the language “referentially.” The understanding that words
refer to things or events in the real world is one of the
key characteristics of human language. Among other things, referential
understanding enables us to discuss things that are not immediately
present or that happened at a different place or time.
Dolphins and Language
Natural language? Dolphins produce various types of sounds,
including clicks, burst-pulse emissions, and whistles. Clicks are
used for echolocation, the dolphin’s form of sonar. Through
echolocation, the dolphin can examine its world through sound, by
listening to the echoes returning from objects struck by the clicks.
Burst-pulse sounds may indicate the dolphin’s emotional state,
ranging from pleasure to anger. However, these type of vocalizations
have been little studied and much remains to be learned about them.
Whistles may be used for communication, but it is still an open
question as to whether, or how much, of whistle communication is
intentional versus unintentional (e.g., rapidly repeated whistling
may be elicited by stress, without any specific intention to convey
that emotional state to others). During the 1960s, researchers attempted
to determine whether the whistle vocalizations might be a form of
language. Investigators recorded whistles from many dolphins in
many different situations, but failed to demonstrate
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sufficient complexity in the vocalizations to support anything approaching
a human language system. Some of the early work instead pointed to
the stereotypy of the whistles from individual dolphins, leading David
and Melba Caldwell to suggest that the whistle functioned principally
as a “signature,” with each individual dolphin producing
a unique signature. Presumably, this enabled that individual to be
identified by others. Other researchers have noted, however, that
there can be a great deal of flexibility in the whistle. Douglas Richards,
James Wolz, and Louis Herman, at the Kewalo Basin Marine Mammal Laboratory
at the University of Hawaii, reported a study showing that a dolphin
could use its whistle mode to imitate a variety of sounds generated
by a computer and broadcast underwater into the dolphin’s habitat.
Peter Tyack later reported that one dolphin could imitate another’s
whistle, thereby possibly referring to or calling that individual.
As was noted earlier, referring symbolically to another individual,
or to some other object or event in the environment, is one of the
basic characteristics of a language. However, we still do not know
to what extent the dolphin’s whistles may be used to refer to
things other than themselves or another dolphin. This is a fruitful
area for additional study, however.
Although the evidence strongly suggests that dolphins do not possess
a natural language, like the case for apes, it is still important
and informative to study whether dolphins might nevertheless be
able to learn some of the fundamental defining characteristics of
human language. Any demonstration of language-learning competency
by dolphins would bear on questions of the origins of human language,
shifting the emphasis from the study of precursors in other hominoid
species to common convergent characteristics in ape and dolphin
that might lead to advanced communicative and cognitive capacities.
Early attempts at teaching language to dolphins. From the
mid-1950s to the mid-1960s, John Lilly promoted the idea that bottlenosed
dolphins (Tursiops truncatus) might possess a natural language.
He based this supposition on this species’ exceptionally large
brain with its richly developed neocortex. He reasoned that the
large brain must be a powerful information processor having capabilities
for advanced levels of intellectual accomplishment, including the
development of a natural language. He set about to uncover the supposed
language. Failing in that quest, he then attempted, also without
success, to teach human vocal language (English) to dolphins he
maintained in his laboratories. Dolphins have a rich vocal repertoire,
but not one suited to the production of English phonemes. The procedures
used by Lilly and the data he obtained were presented only sketchily,
making any detailed analysis of his efforts at teaching language
moot.
In the mid-1960s, Duane Batteau developed an automated system that
translated spoken Hawaiian-like phonemes into dolphin-like whistle
sounds that he projected underwater into a lagoon housing two bottlenosed
dolphins. He then attempted to use these sounds as a language for
conveying instructions to the dolphins. A major flaw in his approach,
however, was that individual sounds were not associated with individual
semantic elements, such as objects or actions, but instead functioned
as holophrases, (complexes of elements). For example, a particular
whistle sound instructed the dolphin to “hit the ball with
your pectoral fin.” Another sound instructed the dolphins to
“swim though a hoop.” Unlike a natural language, there
was no unique sound to refer to hit or ball, or hoop,
or pectoral fin, or any other unique semantic element. Hence,
there was no way to recombine sounds (semantic elements) to create
different instructions, such as “hit the hoop (rather than
the ball) with your pectoral fin.” After several years of effort,
the dolphins were able to learn to follow reliably the holophrastic
instructions conveyed by each of 12 or 13 different sounds. However,
because of the noted flaw in the approach to construction of a language,
the experiment failed as a valid test of dolphin linguistic capabilities.
Kewalo
Basin dolphin language studies. The work on dolphin language
competencies by Louis Herman and colleagues at the Kewalo Basin
Marine Mammal Laboratory in Honolulu was begun in the mid-1970s
and emphasized language comprehension from the start. These researchers,
working principally with a bottlenosed dolphin named Akeakamai housed
at the
laboratory, constructed a sign language in which words were represented
by the gestures of a person’s arms and hands. The words referred
to objects in the dolphin’ habitat, to actions that could be
taken to those objects, and to relationships that could be constructed
between objects. There were also location words, left and right,
expressed relative to the dolphin’s location, that were used
to refer to a particular one of two objects having the same name,
e.g., left hoop vs. right hoop. Syntactic rules, based on word
order, governed how sequences of words could be arranged into sentences
to extend meaning. The vocabulary of some 30 to 40 words, together
with the word-order rules, allowed for many thousands of unique sentences
to be constructed. The simplest sentences were instructions to the
dolphin to take named actions to named objects. For example, a sequence
of two gestures glossed as surfboard over directs the dolphin
to leap over the surfboard, and a sequence of three gestures glossed
as left Frisbee tail-touch directs the dolphin to touch the
Frisbee on her left with her tail. More complex sentences required
the dolphin to construct a relationship between two objects, such
as taking one named object to another named object or placing one
named object in or on another named object. To interpret relational
sentences correctly, the dolphin had to take account of both word
meaning and word order. For example, a sequence of three gestures
glossed as person surfboard fetch tells the dolphin to bring
the surfboard to the person (who is in the water), but surfboard person
fetch, the same three gestures rearranged, requires that the person
be carried to the surfboard. By incorporating left and right
into these relational sentences, highly complex instructions could
be generated. For example, the sequence of five gestures glossed as
left basket right ball in asks the dolphin to place the ball on
her right into the basket on her left. In contrast, the rearranged
sequence right basket left ball in means the opposite, “put the
ball on the left into the basket on the right.” The results published
by Louis Herman, Douglas Richards, and James Wolz showed that the
dolphin was proficient at interpreting these various types of sentences
correctly, as evidenced by her ability to carry out the required instructions,
including instructions new to her experience. These were the first
published results showing convincingly an animal’s ability to
process both semantic and syntactic information in interpreting language-like
instructions. Semantics and syntax are considered core attributes
of any human language.
Ronald Schusterman and Kathy Krieger tested whether a California
sea lion named Rocky might be able to learn to understand sentence
forms similar to those understood by the dolphin Akeakamai. Rocky
was able to carry out gestural instructions effectively for simpler
types of sentences requiring an action to an object. The object
was specified by its class membership (e.g., “ball”) and
in some cases also by its color (black or white) or size (large
or small). In a later study, Schusterman and Robert Gisiner reported
that Rocky was able to understand relational sentences requiring
that one object be taken to another object. These reports suggested
that the sea lion was capable of semantic processing of symbols
and, to some degree, of syntactic processing. A shortcoming of the
sea lion work, however, was the absence of contrasting terms for
relational sentences, such as the distinction between “fetch”
(take to) and “in” (place inside of or on top) demonstrated
for the dolphin Akeakamai. Additionally, unlike the dolphin, the
sea lion’s string of gestures were given discretely, each gesture
followed by a pause during which the sea lion looked about to locate
specified objects before being given the next gesture in the string.
In contrast, gestural strings given to the dolphin Akeakamai were
without pause, analogous to the spoken sentence in human language.
Further, Rocky did not show significant generalization across objects
of the same class (e.g., different balls), but unlike the dolphin
seemed to regard a gesture as referring to a particular exemplar
of the class rather than to the entire class. Thus, although many
of the responses of the sea lion resembled those of the dolphin,
the processing strategies of the two seemed different, and the concepts
developed by the sea lion appeared to be more limited than those
developed by the dolphin.
Akeakamai’s
knowledge of the grammar of the language. As a test of Akeakamai’s
grammatical knowledge of the language she had been taught, Louis
Herman, Stan Kuczaj, and Mark Holder constructed anomalous gestural
sentences. These were sentences that violated the syntactic rules
of the language or the semantic relations among words. The researchers
then studied the dolphin’s spontaneous responses to these sentences.
For example, the researchers compared the dolphin’s responses
to three similar gestural sequences: person hoop fetch, person
speaker fetch, and person speaker hoop fetch. The first sequence
is a proper instruction; it violates no semantic or syntactic rule
of the learned language. It directs the dolphin to bring the hoop
to the person, which the dolphin does easily. The second sequence
is a syntactically correct sequence but is a semantic anomaly inasmuch
as it directs the dolphin to take the underwater speaker, firmly
attached to the tank wall, to the person. The dolphin typically
rejects sequences like this, by not initiating any action. The final
sequence is a syntactic anomaly in that there is no sequential structure
in the grammar of the language that provides for three object names
within a sequence. However, embedded in the four-item anomaly are
two semantically and syntactically correct three-item sequences,
person hoop fetch and speaker hoop fetch. The dolphin
in fact typically extracts one of these subsets and carries out
the instruction implicit in that subset, by taking the hoop to the
person or to the underwater speaker.
These different types of responses revealed a rather remarkable
and intelligent analysis of the sequences. Thus, the dolphin did
not terminate her response when an anomalous initial sequence such
as person speaker was first detected. Instead, she continued
to process the entire sequence, apparently searching backward and
forward for proper grammatical structures as well as proper semantic
relationships, until she found something she could act on, or not.
This analytic type of sequence processing is part and parcel of
sentence processing by human listeners.
Understanding of symbolic references to absent objects.
Louis Herman and Paul Forestell tested the dolphin Akeakamai’s
understanding of symbolic
references to objects that were not present in the dolphin’s
habitat at the time the reference was made. For this purpose, they
constructed a new syntactic frame consisting of an object name followed
by a gestural sign glossed as “Question”. For example,
the two-item gestural sequence glossed as basket question
asks whether a basket is present in the dolphin’s habitat.
The dolphin could respond Yes by pressing a paddle to her
right or No by pressing a paddle to her left. Over a series
of such questions, with the particular objects present being changed
over blocks of trials, the dolphin was as accurate at reporting
that a named object was absent as she was at reporting that it was
present. These results gave a clear indication that the gestures
assigned to objects were understood referentially by the dolphin,
i.e., that the gestures acted as symbolic references to those objects.
Interpreting
language instructions given through television displays.
The television medium can display scenes that are representations
of the real world, or sometimes of imagined worlds. As viewers,
we understand this and often respond to the displayed content similarly
to how we might respond to
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the real world. We of course understand that it is a representation,
and not the real world. It appears, however, that an appreciation
of television as a representation of the real world does not come
easily to animals, even to apes. Sue Savage-Rumbaugh wrote in her
book, Ape Language, that chimpanzees show at most a fleeting
interest in television, and that from their behavior it was not
possible to infer that they were seeing anything more than changing
patterns or forms. Her own language -trained chimpanzee subjects,
Sherman and Austin, only learned to attend to and interpret television
scenes after months of exposure in the presence of human companions
who reacted to the scenes by exclaiming or vocalizing at appropriate
times. Louis Herman, Palmer Morrel-Samuels and Adam Pack tested
whether the dolphin Akeakamai might respond appropriately to language
instructions delivered by a trainer whose image was presented on
a television screen. Akeakamai had never been exposed to television
of any sort previously. Then, for the first time, the researchers
simply placed a television monitor behind one of the underwater
windows in the dolphin’s habitat and directed Akeakamai to
swim down to the window. On arriving there she saw an image of the
trainer on the screen. The trainer then proceeded to give Akeakamai
instructions through the familiar gestural language. The dolphin
watched and then turned and carried out the first instruction correctly
and also responded correctly to 11 of 13 additional gestural instructions
given her at that same testing session. In further tests, Akeakamai
was able to respond accurately even to degraded images of the trainer,
consisting, for example, of a pair of white hands moving about in
black space. The overall results suggested that Akeakamai spontaneously
processed the television displays as representations of the gestural
language she had been exposed to live for many years previously.
Implications
The results of the language comprehension work with the bonobo
chimpanzee and the dolphin Akeakamai show many similarities, especially
in the receptivity of the animals to the language formats used and
in their proficiency at responding to sequences of symbols. The
dolphin has been tested in more formal procedures than has the bonobo,
leading to a fuller understanding of the dolphin’s grammatical
competencies than has been attained for the chimp. The findings
with the bottlenosed dolphin are in keeping with many other demonstrations
of the cognitive abilities of this species. The advanced cognitive
abilities of apes are also well documented. An early summary by
Herman (1980, p. 421) still seems appropriate to accommodate the
convergent cognitive and language-learning abilities of ape and
dolphin: “The major link that cognitively connects the otherwise
evolutionarily divergent (dolphins)... and primates may be social
pressure--the requirement for integration into a social order having
an extensive communication matrix for promoting the well-being and
survival of individuals…. Effective functioning in such a society
demands extensive socialization and learning. The extended maturational
stages of the young primate or dolphin and the close attention given
it by adults and peers…provide the time and tutoring necessary
for meeting these demands. In general, high levels of parental care
and high degrees of cortical encephalization go together….
It is not difficult to imagine that the extensive development of
the brain in (dolphins)…and the resulting cognitive skills
of some members of this group, have derived from the demands of
social living, including both cooperation and competition among
peers, expressed within the context of the protracted development
of the young. These cognitive skills may in turn provide the behavioral
flexibility that has allowed the diverse family of (dolphins)…to
successfully invade so many different aquatic habitats and niches.”
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