NIH funded study: Infants with responsive parents form complex sounds sooner
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Barrett Whitener: A new study suggests that how parents respond to their infants’ babbling sounds may foster their infants’ language skills. Playfully mimicking or returning infant babbling lets the child know that he or she can communicate, and this knowledge helps the infant learn the complex sounds that make up speech. From the National Institutes of Health, I’m Barrett Whitener. This is Research Developments, a podcast from the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development, the NICHD.
With me today is study author, Dr. Julie Gros-Louis, Assistant Professor in the Department of Psychology at the University of Iowa.
Infants whose mothers returned their babbling sounds showed a more rapid increase in what linguists call “advanced consonant-vowel vocalizations,” babbling that sounds more like spoken words. In contrast, infants whose mothers instead directed their infants’ attention to something else did not progress as rapidly in language and communication skills.
Thank you for joining us today, Dr. Gros-Louis.
Julie Gros-Louis: Thanks for having me.
Mr. Whitener: Why did you look at the possible effects of parents’ vocal responses to their infants’ vocal sounds as a separate, distinct category from the parents’ other responses, such as gesturing or looking in a certain direction?
Dr. Gros-Louis: Well, there’s a couple of reasons. One, there was a prior experimental study that had looked at parents’ responses to infants’ vocalizations, and it showed that there were effects of parent social responses on infants’ vocal production. So the infants produced more speech-like sounds when their parents responded contingently—that basically means immediately after their infants vocalized. They produce more sounds like “ba,” “da,” those consonant-vowel, syllable-like sounds that you mentioned earlier. So, that was one reason: we wanted to follow up on this experimental study, and in that study, there were not specific vocal responses of parents, but rather non-vocal responses.
But we were interested in looking at whether parents’ imitative responses or potentially other types of vocal responses that were related to what infants were looking at or playing with at the time they vocalized, could help boost speech development, and also language development. So that was the first reason. We wanted to look over a longer developmental period to see if this social responsiveness, or what’s termed “social shaping,” could influence the development of speech and language.
Now, a second reason is, we were interested in looking at these vocal responses to infants’ vocalizations as a means of letting infants know that their vocal production was effective in eliciting responses. So, you could think about it as, like, a conversation. If infants vocalize and parents respond vocally, particularly about what it seems like their infants are talking about—so, what they’re interested in, what they’re looking at, or what they’re playing with when they vocalize—infants might learn the potential function of those vocalizations as a means to communicate.And that’s something that hadn’t been looked at previously.
So there’s many, many prior studies that have looked at language development and language outcome, which was also part of this study, but another thing we looked at was how infants who have received responses potentially increase their use of vocalizations in social interactions—sort of like a social tool, that’s the way that some researchers have talked about it previously.
Mr. Whitener: How did you conduct the study?
Dr. Gros-Louis: So, this was a longitudinal study, and that means that it was conducted over a period of time, and in this particular study we had mothers and infants come into the lab playroom for 30 minutes every other week over a period of 6 months. The study started when infants were 8 months old and finished when they were 14 months old, so there were two monthly visits for those 6 months.
Basically, we just had mothers and infants play in a playroom. It had toys and we told them, just play as you would at home. These were what people would call naturalistic interactions, as natural as you can get. It’s a lab playroom, but they’re free to do what they want. And what we looked at specifically, then, was when infants vocalize during these interactions, we noted where they were looking—so whether they were looking at their mother, or looking at a toy—and we also then looked to see if mothers responded immediately following those vocalizations of their infants.
So, we were interested to see how frequently mothers responded contingently, again immediately following the vocalization of their infant, and also how they responded: so, how often, and also what types of responses they produced.
And over the course of those six months, we were interested in looking at specifically if mothers who responded more frequently and about what their infants seemed to be communicating about, if those mothers would help increase the language skills of their infants or their speech skills over the course of those 6 months.
Mr. Whitener: Now you mention in the study that you coded the infants’ vocalizations or categorized them, using a broad classification that, to put it really simply, distinguishes simpler sounds from more advanced vocalizations. Can you say just a little bit about how you classified the different kinds of sounds and drew the conclusion that this was a speech-like response, if you will?
Dr. Gros-Louis: Yeah, so the vocalizations, the categories of vocalizations that we coded were very broad, basic categorizations of sounds that had a consonant in them, so a consonant and vowel together, which is similar to a speech-like syllable; so an example would be “ba,” or “da,” or “ma.” Sometimes those might be repeated, like “da-da-da-da.” And the other category that we coded were vowel-like sounds, so the sounds that lack that consonant, that don’t have the consonant. So, those are considered to be by researchers in the field, less developmentally-advanced. Infants are progressing over the first year toward more speech-like syllable sounds, and those are considered more developmentally advanced.
So, we just classified them as vowel-like or consonant-vowel, syllable-like sounds, and those were the two classifications that we used.
I should also add, I should mention, 1 month after the study ended, so when infants were 15 months of age, we asked mothers to fill out the MacArthur Communicative Development Inventory; it’s MCDI for short. The MCDI is a language inventory, so it indicates what words children have in their vocabulary, and also what words they comprehend, but maybe they don’t say yet. It also measures gestures that they use. It basically gives researchers a sense of how many words infants know, how many words they know in terms of what they understand, compared to what they can also say. So we use that as an outcome measure to look at how parents’ responses, or mothers’ responses, influence language outcomes, in addition to the changes in the syllable-like sounds.
Mr. Whitener: So, just to clarify for parents and caregivers who may be listening, if I understand you correctly, it’s not that the children whose mothers did not vocalize back to them immediately, not that those children ultimately had poorer language development, it’s just that those whose mothers did respond had that development more quickly?
Dr. Gros-Louis: Yes, that’s correct. That’s a really good point to make. So, the mothers who responded to their infants’ vocalizations right after they vocalized, and also responded about what the infant was looking at, or again, what they were playing with, what they seem to be interested in, those infants had higher vocabulary and more gestures in their communication at 15 months of age. But it wasn’t the case that infants whose mothers were less responsive had significant deficits in language. It just helped accelerate those infants whose mothers were very responsive.
Mr. Whitener: So, what would you say are the implications of your study for parents and caregivers? Is it simply a matter of paying more attention and responding when a child babbles, and pointing to whatever they’re looking at, etc.?
Dr. Gros-Louis: Yeah, I think that’s one good take-home point, and I should also mention that infants whose mothers were more responsive to their vocalizations actually showed an increase in the vocalizations that they directed to their mother or the ones that they produced when they were looking at their mother. So again, if you think about this as influencing communication in general as opposed to just language or just speech-like syllables, getting responses to vocalizations tells the infant that their vocalizations are effective in interactions. They get something for them; they get a response. So, what happens is, those infants increase their vocalizations and have more interactions with their mothers surrounding those vocalizations, and so they have more opportunities for learning.
And so, paying more attention to the babbling and as opposed to just cooing or making some noise back, sort of responding as if the child is actually communicating something, or talking about something, by telling them about what they’re looking at—or not even just labeling, it’s really having a conversation with your infant. And that’s something to keep in mind in general, that infants are very active learners and that’s something that cuts across all aspects of development. Infants act in their environment. In this case, they’re acting in these social interactions with their mother by vocalizing. And then the responses they get can influence further development.
So rather than thinking of infants as passive, and just sitting there waiting to absorb whatever you teach them, respond to the things that they do and in turn that will influence their development.
Mr. Whitener: Do your findings have other implications for things such as the development of communication generally?
Dr. Gros-Louis: Yeah, so a long-standing theoretical perspective or theory of development of language is that it’s based on innate mechanisms and that basically means that there’s just a built-in program that sort of unfolds, let’s say, during development to allow young children to learn language. And in contrast to that view that’s been held for quite some time, this indicates that parents can actually influence and accelerate their child’s speech and language development, so they can have an influence through these social responses. Everything isn’t just built in from the start.
Mr. Whitener: You mentioned in the study that it will be ideal to work with a larger sample of folks going forward and their infants. Can you talk about your plans in that regard?
Dr. Gros-Louis: Yes, I should mention, we actually have recently finished a study that we’re working on analyzing and writing up a paper about, where we looked at parent-infant interactions. We looked at mothers and infants interacting, and then separately the fathers and infants interacting, and we were exploring the same types of questions. So, asking when infants vocalized, how did their mothers respond, and compared that to how fathers responded, and then also looking at language outcomes.
So as I said, we’re still in the process of analyzing that data, but I do know at this point that mothers and fathers, at least in our sample of about 90 people, mothers and fathers showed similar levels of responding. In terms of the frequency of responding, it seems to be similar, but there’s some slight differences in how parents respond. And we don’t know yet what implication that is. We don’t know what the outcome is yet, but it’s hopefully coming in the next month or so, as we finish our data analysis and writing up of this paper.
Mr. Whitener: Well, that’s great. We’ll look forward to reading the next stage of your progress and keeping up with this fascinating research.
Dr. Gros-Louis: Well, thank you very much.
Mr. Whitener: I’ve been speaking with Dr. Julie Gros-Louis, lead author of the study, “Maternal Responsiveness and the Development of Directed Vocalizing and Social Interactions,” which was published in the journal Infancy.
About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute's website at http://www.nichd.nih.gov/.