Hey! What’s that sound?!

#freshfromthelab. Victoria Mousley, first-year PhD student at University College London, on her plans for investigating infant language perception.

Have you ever envied how quickly kids learn new languages? It is so much harder in adulthood! There’s some interesting science behind this.

It’s true that adults struggle to discriminate sounds of foreign languages. For example, I am a native English-speaking adult, so I struggle to perceive the sounds of Hindi or Arabic. However, babies younger than 6 months old can hear the subtle differences in the sounds of all the world’s languages. Babies at this age are sometimes called universal listeners." However, this skill doesn’t last very long — by the end of the first year, babies perform like adults, perceiving only the naturally occurring sounds in their native language(s).

Some researchers think that bilingual babies, raised with exposure to two languages from birth, may possess some language processing advantages." This might make sense considering that they need to learn two languages rather than one, but they develop their language skills along the same timeline as monolingual infants. Because their language input is split between two languages, they also get less exposure to each language than monolingual infants do. How do they sort themselves out so quickly? We have no idea, but researchers are working hard to learn more.

People think that the demands of learning two languages could allow bilingual babies to remain “flexible” in their foreign-language-listening skills. Monolinguals lose the ability to perceive foreign language sounds by 12 months, but bilingual babies might not. In my PhD, I’m hoping to find out!

We will be collecting data from both monolingual and bilingual babies between 15 and 18 months old. Baby will sit on mum’s lap and watch several minutes of sounds and videos on a TV screen. Most importantly, we will play a series of Hindi language sounds for the babies. English native adults cannot perceive the difference between these two phonemes, called a dental "ta" and retroflex "Ta".

These cartoons are drawn from x-rays of native Hindi speakers producing the dental "ta" vs retroflex "Ta". The dental sound is shown on the left. It is produced in English, French, and many other European languages. The retroflex "Ta" is on the right — you can see that the tongue is placed a bit farther back on the roof of the mouth. When I do it, it sounds more like “Da” than it should, because I am a native English speaker. If you want to play around with these kinds of contrasts, try Googling “[insert foreign language] phonetic contrasts.” There are loads! Click here for some Hindi examples you can learn on YouTube.

During our study, the first technique we will use is called “eye-tracking” (watch this space for an upcoming post on the details of this technique.)

The eye-tracker shows us where babies look and for how long, which can tell us what babies can hear and what they can’t. Babies will be shown a black and white checkerboard on a TV screen while they listen to different sounds. We expect that the English monolingual babies will not be able to hear the dental "ta" vs retroflex "Ta" contrast, meaning that they will look at the screen for the same amount of time for all the syllables. If the bilingual babies can hear the differences, which we expect they will, they will look at the TV screen longer for the retroflex "Ta" than the monolingual babies. This is basically the baby saying, “Hey! What’s that sound?!” Eye-tracking only tells us when babies are looking or not looking, but it can’t tell us anything about what their brains are doing to arrive at their behaviour.

So, we will also use electroencephalogram (EEG) to compare what the babies’ brains are doing when they are processing the sounds of a foreign language. The EEG looks like a hairnet with little buttons on it, as you can see in the picture. It is a safe and easy way for us to measure babies' brain waves. We expect that the bilingual babies brains will show more sensitivity to an unfamiliar (Hindi) sound, almost “hearing it more” than the monolingual babies.

You may be asking yourself, “Well, is it better to be more sensitive to foreign languages?” We’re not sure! To examine this question, I will look at measures of baby’s early learning and language skills, both when they visit our lab and several months after they’ve left. I will look to see whether anything we see in the babies’ looking behaviours or their brain waves correspond with their later achievements in language production. I’ll keep you posted on the project’s progress!

Author: Victoria Mousley

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