Soderstrom – studying infant language preferences

My name is Melanie Soderstrom. I’m an associate professor here at the University of Manitoba in the department of psychology and I run the baby language lab which is an experimental research lab with infants where we look at how babies learn their first language.  

We bring babies into the lab and we play speech sounds for them and then we measure their interest in what they’re listening to and we use that to learn about what they understand about language, what they prefer about language. 

The first study uses a method called the head-turn preference procedure and the idea with the head-turn preference procedure is that we associate the speech sounds with a visual stimulus, just a visual display. And in the old days that was actually a flashing light. Now we do it-usually do it with video screens and so it’s a flashing circle that changes to a checkerboard pattern. And it’s just a way of measuring what the baby is interested in listening to. 

So if they turn their head the speech sound plays. If they turn their head away after a certain amount of time the speech sound stops. And the babies learn really quickly that they can control what they’re listening to.  

So the baby comes into the lab. They’re seated on the mom’s lap. The mom is wearing a set of headphones that play kind of a weird mix of music and speech to try and mask what’s being played so that they don’t accidentally influence the baby’s behaviour. And that’s really important. And then the experimenter is in another room so they also can’t hear what’s being played and again bias things. And then when the baby’s looking forward the screen on the side comes on. The baby looks to the side and then it changes to the checkerboard and we play the speech and like I said, as long as they’re looking towards the screen the sound plays and if they look away the sound stops.  

So the longer that they look towards the screens the more interested they are and so we can compare different types of speech. So in this particular study, we’re looking at baby’s interest in something called infant-directed speech. So the way that we talk to babies that’s different from the way that we talk to adults.  

It’s been known for a number of decades that we speak differently to babies than to adults. And so there’s been a lot of research looking at the different properties, the fact that we use a higher pitch and a more variable pitch, the fact that we speak more slowly and with more of a happy, positive affect and a number of other characteristics. And there’s a lot of research supporting the idea that this is actually beneficial for babies in learning language. And then together with that, there’s also a growing body of research that shows that babies prefer to listen to speech that’s in that style versus in the adult-directed style which is kind of more monotone and longer sentences and things like that.  

So they’re hearing speech that’s in this infant-directed speech mode and other speech that’s more directed at an adult and we look to see whether they prefer the speech sounds in infant-directed speech over adult-directed speech. 

In this particular study, the speech they’re hearing is Norwegian because we’re also looking at differences across languages and language communities in infants’ preference.  

We’re measuring the length of the looking time on a given trial and if that looking time is longer then we interpret that to mean that the baby prefers that speech stimulus than if they look for a shorter period of time.  But obviously, we can’t get into the baby’s head and this is an inference that we’re making. This is one of the things that makes research with infants much different from with adults or even certain aged children where you can actually ask them, “hey, do you like this or do you not like this?” We have to make these inferences based on their behaviour and what can babies do. They can suck on things, they can look at things, they can grab for things. So those are the things that we measure.