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Study: Rats have head for language
Three types of mammals shown to have such language skills
January 9, 2005
WASHINGTON -- Rats can use the rhythm of human
language to tell the difference between Dutch and Japanese, researchers in Spain
reported on Sunday.
Their study suggests that animals, especially mammals, evolved some of the
skills underlying the use and development of language long before language
itself ever evolved, the researchers said.
It is the first time an animal other than a human or monkey has been shown to
have this skill.
"These findings have remarkable parallels with data from human adults, human
newborns, and cotton-top tamarins," the researchers wrote in their report,
published in the "Journal of Experimental Psychology: Animal Behavior
Processes," which is published by the American Psychological Association.
For their study neuroscientists Juan Toro and colleagues at Barcelona's
Scientific Park tested 64 adult male rats. They used Dutch and Japanese because
these languages were used in earlier, similar tests, and because they are very
different from one another in use of words, rhythm and structure.
The rats were trained to respond to either Dutch or Japanese using food as a
Then they were separated into four groups -- one that heard each language spoken
by a native, one that heard synthesized speech, one that heard sentences read in
either language by different speakers and a fourth that heard the languages
played backwards. Rats rewarded for responding to Japanese did not respond to
Dutch and rats trained to recognize Dutch did not respond the spoken Japanese.
The rats could not tell apart Japanese or Dutch played backwards.
"Results showed that rats could discriminate natural sentences when uttered by a
single speaker and not when uttered by different ones, nor could they
distinguish the languages when spoken by different people," the researchers
wrote. Human newborns have the same problem, although tamarins can easily tell
languages apart even when spoken by different people, the researchers said.
"It was striking to find that rats can track certain information that seems to
be so important in language development in humans," Toro said in a statement.
The study shows "which abilities that humans use for language are shared with
other animals, and which are uniquely human. It also suggests what sort of
evolutionary precursors language might have," he added.