|Rats show off language skills
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|Автор:||NikSt [ Пн янв 10, 2005 21:14 pm ]|
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Rats show off language skills
23:00 09 January 2005
NewScientist.com news service
Rats can tell the difference between Dutch and Japanese, suggests a new study. But it is not because some spy agency has bioengineered them to eavesdrop on conversations in Tokyo or Amsterdam.
They are simply recognising the difference in rhythmic properties of the languages, says Juan Toro, a neuroscientist at the University of Barcelona in Spain, whose study is part of an effort to trace the origins of the skills that humans use to analyse speech.
Human infants are extremely sensitive to the rhythmic regularities of language, which researchers think may help infants to break sound into patterns they can decipher as words. Earlier experiments showed that both tamarin monkeys and human infants can discriminate between Dutch and Japanese - two languages with rhythmic content that differs greatly.
Toro's team trained rats to recognise either Dutch or Japanese - by pressing a lever in response to a short sentence - and then exposed them to sentences they had not heard before, in both languages.
They found that the rats responded significantly more often to the language they had been trained in - as long as the sentences were computer-synthesised or both languages were spoken by the same person. However, the rats could not tell the difference if the sentences were played backwards or were spoken by different people.
Feeling the rhythm
Having different people say the words adds irrelevant information that "makes the task too difficult for rats", Toro says. But playing sentences backwards is more important to understanding speech because it alters rhythmic patterns.
"We still don't know what exactly is lost" by playing speech backwards, Toro told New Scientist, but it is enough to prevent both human infants and tamarin monkeys from telling Dutch and Japanese apart.
Human infants are unable to distinguish between languages with little difference in rhythmic properties, such as English and Dutch, or Spanish and Italian. Rats have not been tested with these pairs of languages, and are the only non-primates yet tested with Dutch and Japanese.
But rats' ability to detect rhythmic patterns does not mean they are evolving language. It probably means they rely on "some mechanism suited for auditory processing in general", Toro says.
Rat ancestors may have evolved that ability to sense sound patterns that might warn of predators approaching or changing predator behaviour. Humans may have evolved similar skills for similar reasons, before the ability was co-opted for other purposes, such as helping in the development and decoding of speech.
Journal reference: Journal of Experimental Psychology: Animal Behavior Processes (vol 31, p 95)
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