Rats can tell two languages apart from speech cues, sharing an ability with humans and monkeys
They’re the third type of mammal shown to have this skill
Mammals other than humans can distinguish between different speech patterns. Neuroscientists in Barcelona report that rats, like humans (newborn and adult) and Tamarin monkeys, can extract regular patterns in language from speech (prosodic) cues. The report appears in the January issue of the Journal of Experimental Psychology: Animal Behavior Processes, which is published by the American Psychological Association.
This study of 16 rats per each of four conditions showed that they were able to pick up enough cues from the rhythm and intonation of human speech to tell spoken Dutch from spoken Japanese. After the researchers trained rats to press a lever when hearing a synthesized five-second sentence in Dutch or Japanese, they tested the rats’ response to the alternative language. Rats rewarded for responding to Japanese did not respond to Dutch and vice versa. They pressed the lever only for the language to which they’d been exposed. What’s more, the rats generalized the ability to differentiate to new Dutch and new Japanese sentences they had not heard before.
This special ability to detect the features that distinguish one type of speech from another – enabled by a test using two very different spoken languages – has now been documented in three different mammalian species: Humans (both newborn and adult), Tamarin monkeys, and now rats. Scientists study Tamarin monkeys because they can use the same kinds of experiments that they use for infants, allowing for direct comparison. The rats were the first non-primate mammal studied; research on non-mammalian species (such as songbirds) may shed light on whether this ability is unique to mammals.
The rats’ linguistic sophistication was limited. When experimenters used different humans to speak each sentence, the rats found it much hard to tell the languages apart. Humans, even in early infancy, can overcome this problem – and only get better at it by learning a lexicon and syntax, phonology (letter sounds), word segments, and semantic information (what words mean).
Author Juan Toro, who is about to earn his PhD, says the results were surprising. "It was striking to find that rats can track certain information that seems to be so important in language development in humans," he says. The research, he adds, 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."
Toro cautions that just because the rats share an ability with humans doesn’t mean they use it the same way. He says, "Rats have not evolved the ability to track prosodic cues for linguistic requirements. It is more likely that they do it as a byproduct of other abilities that have some evolutionary relevance for them. The idea that species can use certain structures for a different function than that for which they evolved is not new. For example, human newborns coordinate all the speech information they take in to eventually make sense of language, something that a rat is not likely to do."
It is very likely, he and his co-authors suspect, that the ability to tell apart two different languages is a byproduct of more general perceptual abilities used for detecting time order through hearing – a useful adaptation for the rat. Thus, he adds, "rats can co-opt these abilities to differentiate sentences by detecting their prosodic regularities."
Pam Willenz | EurekAlert!
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes
The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....
Larsen C Ice Shelf rift finally breaks through
A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...
Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision
Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...