Ever noticed how when you speak to your little one you use a different voice? Often higher pitched, slower, repetitive and rhythmic in a “sing-song” kind of way? Well, that babytalk, or what we in developmental science call infant-directed speech, is observed in cultures across the globe and is thought to be a consequence of evolution. Being part of our evolutionary profile infant-directed speech needs to have an adaptive purpose. It needs to increase the survival of our offspring. So, what is the purpose of infant-directed speech?
Historically, infant-directed speech has been considered to help with infant emotional regulation. Just think, you’ll often use this way of talking a little more when you are soothing your child. But actually, a recent resurgence in the study of infant-directed speech is shedding new light on its role in infant cognitive development. At this year’s International Congress of Infant Studies, Professor Goldstein from Cornell University summarised his recent findings on the contributions of both Infant directed speech and infant directed movement on infant word learning.
In the process of learning new words, your infant must overcome not only cognitive challenges (the mental capacity to acquire the knowledge) but also attentional challenges (staying engaged long enough to the appropriate stimuli to put two and two together). Overcoming the latter is of upmost importance for efficient word learning, and is a possibly an evolutionary purpose of infant-directed speech and movement. We as caregivers direct our little one’s attention to objects in the environment in a baby-friendly manner whilst labelling objects, ultimately facilitating word learning. Studies demonstrate infant-direct speech not only to go above and beyond normal (or adult directed speech) for engaging attention to but it also sensitizes infants to stimuli they have become habituated it. This means that when an object is no longer new to an infant, they will become habituated and spend less time looking at it. But when infant-directed speech occurs whilst presenting this habituated stimuli to the infant, looking time increases, even when the infant directed speech no longer occurs. The infant has become sensitized and dishabituated to the object – they will start paying attention to the object again. This is not the case for adult-directed speech where once the speech no longer occurs, the infant will disengage with the object. These findings highligh the importance of infant directed speech in directing and sustaining infant attention to the environment.
In addition to infant-directed speech for manipulating infant attention, the way we move or position objects in the environment (infant directed movement) plays a key role in word learning. For example, if you and your baby are playing with a stuffed toy, you’d likely move the toy around them in an exaggerated way, often in time with the rhythm of your Babytalk. These behaviours that often do naturally without much thought play guide the infant’s attention to objects in the environment as well as enable the association between visual and auditory stimuli – all of which is crucial for accurate word learning. By moving the toy in an engaging manner, whilst engagingly talking about the toy (often repeating the toys name), the child will quickly pick up on the association between the toy and the toy’s name.
Demonstrating the importance of infant directed movement alongside infant directed speech, Professor Goldstein developed a training and comprehension study testing the effects of infant directed behaviours on infant word learning at 13-months. During the training phase of the study, infants would be presented with a new object. The researcher would then label this new object with a new word. For example, the researcher would say “Here is a Dax. Look at the Dax. It is a Dax” while holding and moving a toy the child had never seen before. “Dax” being the new word and the toy being the new object. The researcher would either use infant directed speech or monotonic adult directed speech combined with either infant directed movement of the toy or no movement of the toy; giving us four combinations (or conditions) to which the infant participant was assigned. Once they had undergone the training, the infant’s word/object comprehension was tested, both immediately after the training and then 24 hours later. To assess if the infant had learnt the word/object, they were asked in the type speech in which they were trained (IDS or adult directed speech) to place the new object (which was presented on the table in front of them alongside another object) in a basket.
Interestingly, results demonstrated that for both the immediate and 24-hour delayed comprehension task the infant’s word/object learning was not influenced by the type of speech they were exposed to during training. Infants learnt the new word equally well with infant directed speech and adult directed speech. But, when the infant was exposed to infant directed speech and no movement of the toy, they performed worse on the compression task than all other combinations of training. What Professor Goldstein thinks is going on here is that infant directed speech is drawing the infant’s attention to the speakers face and social cues. Without the addition of infant directed movement, the infant will not attend to the object and ultimately will not learn the name of the object as well.
So, next time catch yourself speaking in that high pitch voice, remember you’re doing something awesome! You’re directly contributing to your baby’s development!
For more information on infant directed speech, check out this awesome video summary from Dr Marina Kalashnikova from the BabyLab at Western Sydney University.