A pair of researcher from the University of Alabama has shown that gerbils can be trained to recognise human vowel sounds.
Joan Sinnott and Kelly Mosteller have found that gerbils can easily distinguish between vowels like an 'oo' (as in 'you') and an 'ee' (as in 'me').
The researchers, however, do not have any plans to train gerbils to understand words or sentences because they believe that the animal can never understand the semantics of human speech.
They say that their work will help them study how human infants discriminate between sounds before they become part of a known language, for a good animal model may provide a useful way of looking at this question.
Sinnott says that at the outset, she involved monkeys in her research. But since monkeys were too smart, she switched to gerbils for her study.
"They (monkeys) can hear all the human phonemes (basic speech sounds) I have tested, even the difficult ones," Nature magazine quoted her as saying.
The researchers began their study by training Mongolian gerbils to understand different vowels — one indicating that the food was in the cup kept in the left-hand side, while the other signifying that the food was in the right-hand cup.
According to them, the gerbils could learn this rule relatively quickly in tests with pairs of ten different vowel sounds.
Sinnott said that just like humans, gerbils too were found to vary in their abilities. She revealed that two of the six gerbils in her group could distinguish many vowel pairs about nine times out of ten, while others performed less well.
However, the overall performance of the subjects was quite good, said the researchers while presenting their findings at the meeting of the Acoustical Society of America in New Orleans last month.
The researchers also studied how and why some vocal sounds are easier to discriminate than others. According to them, there are three main frequency components in human speech: F1, which depends on tongue height; F2, which depends on whether the tongue is at the front or back of the mouth; and a high-frequency component, F3, that can be influenced by tongue curvature.
They found that increasing difference in F2, which is known to be the most important formant for human speech perception, improved the skills to discriminate between sounds in the gerbils.
"It's a very exciting finding for us. This result bodes well for using the gerbil as an animal model for human speech perception," they said.
Since gerbils have short lifespan, the researchers hope that the animals may help them study how aural discrimination changes with age.