[Paleopsych] NYT: Is It Dutch? Japanese? Why Not Ask the Rat?

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Is It Dutch? Japanese? Why Not Ask the Rat?
NYT January 11, 2005
By NICHOLAS BAKALAR

If you talk to a rat, you will not get an answer. But a
team of Spanish neuroscientists has shown that a
well-trained rat may be able to determine what language you
are speaking.

Every language has distinctive rhythms and intonations, and
awareness of them is an important step in acquiring
language. Only humans can learn to speak, but it has been
demonstrated that tamarin monkeys, like newborn human
infants, can distinguish the unique rhythms of a language
even though meaning escapes them.

In other words, they know when someone is speaking their
language, even though they have no idea what is being said.
Researchers have theorized that this ability extends to
other mammals as well, but until now no nonprimate has ever
demonstrated the capacity.

In the new study, led by Juan Toro, a doctoral candidate at
the University of Barcelona, researchers found that rats
trained in either Dutch or Japanese appeared able to
distinguish the two languages. The rats were trained by
having them listen to synthesized sentences in the
languages. Dutch and Japanese were chosen because of their
vastly different rhythms. The sentences had no semantic
content, but were intended to reproduce the rhythms of the
language without using any real words.

This simplified form of language, when spoken in a
synthesized voice, leaves only rhythm as a cue, eliminating
complicating factors like semantic content or the quality
of the voice of a particular speaker.

For the Dutch group, the rats were rewarded with food only
when they pressed a lever after hearing Dutch sentences.
The Japanese group was rewarded only after hearing Japanese
sentences. Eventually, both groups learned to press the
lever only when hearing a sentence in their own languages.

Next, the rats listened to four synthesized sentences in
the language they had not learned. When the Dutch mice were
presented with Japanese sentences, they showed no
recognition; when the Japanese mice were presented with
Dutch, they were similarly baffled. But when presented with
a sentence in their own languages, even a sentence they had
never heard before, the rats recognized the characteristic
rhythm and pressed the lever correctly.

The researchers said the rats appeared to have generalized
some of the rules of their language and, at least in this
limited way, were able to understand an entirely new
sentence, a distinctive mark of language acquisition. When
the researchers played the same sentences with the tape
running backward, the rats were unable to understand what
language was being spoken - exactly what happens with
tamarins and human infants.

Rats, of course, have limitations. They had considerably
more difficulty in telling one language from another when
listening to normal speech, especially when uttered by
different speakers, the researchers found. The multiplicity
of cues in ordinary conversation - intonation, the
speaker's sex, pitch and so on - utterly confused them.

Human infants have some difficulty with different voices,
too, but they quickly overcome it, learning to recognize
their own language no matter who is talking and however
varied the pitch and intonation. "What these results
suggest," Mr. Toro said in an e-mail interview, "is that we
share with other animals the ability to perceive some
regularities, such as rhythm, in the speech signal. This is
interesting because several studies with human infants have
shown that these regularities may open the door to language
acquisition."

Does this mean rats and monkeys have the potential to
understand human speech? No, said Mr. Toro. But he added,
"Even though human language is special and does not seem to
have parallels in the communicative systems of other
species, some basic abilities we use for acquiring it may
be present in other animals."

http://www.nytimes.com/2005/01/11/health/11anim.html