- WASHINGTON (Reuters) - Rats
can use the rhythm of human language to tell the difference between Dutch
and Japanese, researchers in Spain reported 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 reward.
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.