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Social
transmission of the spoken word
The starlings'
mimetic repertoires varied consistently by social context: only the birds
in interactive contact mimicked sounds with a clearly human origin. None
of the other subjects imitated such sounds, although all mimicked their
cowbird companions, each other, wild birds, and mechanical noises. For
the purposes of this article, we have elected to focus solely on the actions
of the birds in interactive contact.
All of these birds mimicked human sounds---including
clear words, sounds immediately recognizable as
speech but largely unintelligible, and whistled
versions of songs identified as originating from
a human source---and mechanical sounds whose source
could be identified within the households. For
the three audio taped birds, roughly two-thirds
of their vocalizations were related to the words
or actions of caregivers. The same categories
applied to the remaining five birds, who mimicked
speech, whistles, and human-derived or mechanical
sounds.
Relationships
between starlings and human beings appear to reflect the behavior of birds
in the wild. Hand-reared starlings interact with their human compainions
in terms of the social roles of wild birds. In particular, they learn
by observing vocal and other responses to their own expressive efforts.
Many of
the more impressive properties of the starlings' vocal capacities defy
simple categorization. The most striking feature was their tendency to
mimic connected discourse, imitating phrases rather than single words.
Words most often mimicked alone included the birds' names and words associated
with humans' arrivals and departures, such as "hi" or "good-bye." All
phrases were frequently recombined, sometimes giving the illusion of a
different meaning. One bird, for example, frequently repeated, "We'll
see you later," and "I'll see you soon." The phrase was often shortened
to "We'll see," sounding more like a parental ploy than an abbreviated
farewell. Another bird often mimicked the phrase "basic research" but
mixed it with other phrases, as in "Basic research, it's true, I guess
that's right."
The
audiotapes and caregivers' reports made clear,
however, that nonsensical combinations (from a
human speaker's point of view) were as frequent
as seemingly sensible ones: the only difference
was that the latter were more memorable and more
often repeated to the birds. Sometimes, the speech
utterances occurred in highly incongruous settings:
the bird mentioned above blasted his owners with
"Basic research!" as he struggled frantically
with his head caught in string; another screeched,
"I have a question!" as she squirmed while being
held to have her feet treated for an infection.
The tendency for the birds to produce comical
or endearing combinations did much to facilitate
attention from humans. It was difficult to ignore
a bird landing on your shoulder announcing, "Hello,"
"Give me a kiss," or "I think you're right."
The birds
devoted most of their singing time to rambling tunes composed of songs
originally sung or whistled to them intermingled with whistles of unknown
origin and starling sounds. Rarely did they preserve a melody as it had
been presented, even if caregivers repeatedly whistled the "correct" tune.
The tendency to sing off-key and to fracture the phrasing of the music
at unexpected points (from a human perspective) was reported for seven
birds (no information on the eighth). Thus, one bird whistled the notes
associated with the words "Way down upon the Swa-," never adding "-nee
River," even after thousands of promptings. The phrase was often followed
by a whistle of his own creation, then a fragment of 'The Star-spangled
Banner," with frequent interpositions of squeaking noises. Another bird
whistled the first line of "I've Been Working on the Railroad" quite accurately
but then placed unexpectedly large accents on the notes associated with
the second line, as if shouting, "All the livelong day!" Yet another routinely
linked the energetically paced William Tell Overture to "Rockaby
Baby."
One category
of whistles escaped improvisation. Seven of the eight caregivers used
a so-called contact whistle to call the birds, typically a short theme
(e.g., "da da da dum" from Beethoven's Fifth Symphony). This fragment
of melody escaped acoustic improvisation in all cases, although the whistles
were inserted into other melodies as well. One bird, however, often mimicked
her contact whistle several times in succession, with each version louder
than the preceding one (perhaps a quite accurate representation of the
sound becoming louder as her caregiver approached her).
All the birds
in interactive contact showed an interest in whistling
and music when it was performed. They often assumed
an "attentive" stance, they stood very quietly,
arching their necks and moving their heads back
and forth. The birds did not vocalize while in
this orientation. Records for all eight subjects
contained verbal or pictorial reports of the posture.
Clear mimicry
of speech was relatively infrequent, due in large part to the birds' tendency
to improvise on the sounds, making them less intelligible although definitely
still speech like. Other aspects of their speech imitations were also
significant. First, the birds would mimic the same phrase, such as "see
you soon" or "come here," but with different intonation patterns. At times,
the mimetic version sounded like a human speaking in a pleasant tone of
voice, and at other times in an irritated tone. Second, when the birds
repeated speech sounds, they frequently mimicked the sounds that accompany
speaking, including air being inhaled, lips smacking, and throats being
cleared. One bird routinely preceded his rendition of "hi" with the sound
of a human sniffing, a combination easily traced to his caregiver being
allergic to birds. Finally, the quality of the mimicry of the human voice
was surprisingly high. Many visitors who heard the mimicry "live" looked
for an unseen human. Those listening to tapes asked which sounds were
the starlings' and which the humans', when the only voices were the birds'.
The particular
phrases that were mimicked varied, although a majority fell into the broad
semantic category of socially expressive speech used by humans as greetings
or farewells, compliments, or playful responses to children and pets.
Several of the starlings used phrases of greeting or farewell when they
heard the sound of keys or saw someone putting on a coat or approaching
a door. Several mimicked household events such as doors opening and closing,
keys rattling, and dishes clinking together. One bird acquired the word
"mizu" (Japanese for water), which she routinely used after flying to
the kitchen faucet. Another chanted "Defense!" when the television was
on, a sound that she apparently had acquired as she observed humans responding
to basketball games.
Caregivers
reported that it took anywhere from a few days to a few months for new
items to appear in the birds' repertoires. Acquisition time may have depended
on the kind of material: one of the birds in limited contact, housed with
a new cowbird, learned its companion's vocalization in three days, while
one bird in interactive contact took 21 days to mimic his cowbird companion.
The latter bird, however, repeated verbatim the question, "Does Hammacher
Schlemmer have a toll-free number?" a day after hearing it said only once.
Some whistled
renditions of human songs also appeared after intervals of only one or
two days. An important variable in explaining rate of acquisition and
amount of human mimicry may be the birds' differential exposure to other
birds. The three birds without avian cage mates appeared to have more
extensive repertoires, but they were also older than the other subjects.
The birds
did not engage much in mutual vocal exchanges with their caregivers, that
is, a vocalization directed to a bird did not bring about an immediate
vocal response, although it often elicited bodily orientation and attention.
Thus, the mimicry lacked the "conversational" qualities that have been
sought after in work with other animals (10). As no systematic
attempt had been made to elicit immediate responding by means of food
or social rewards, reciprocal exchanges may nevertheless be possible.
Ongoing human conversation not involving the starlings, however, was a
potent stimulus for simultaneous vocalizing. The birds chattered frequently
and excitedly while humans were talking to each other in person or on
the telephone. The starlings' lively interest and ability to participate
in the activities of their caregivers created an atmosphere of mutual
companionship, a condition that may be essential in motivating birds to
mimic particular models, as indicated by the findings with the birds in
limited and auditory contact. The capacity of starlings to learn the sounds
of their neighbors fits with what is known about their learning of starling
calls, especially whistles, in nature. They learn new whistles as adults
by means of social interactions, an ability that is quite important when
they move into new colonies or flocks (11). Analyses of social
interactions between wild starling parents and their young also indicate
the use, early in ontogeny, of vocal exchanges between parent and young
and between siblings (12). Thus, the capacities identified in the
mimicry of human speech and their dependence on social context seem relevant
to the starling's ecology.
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