Hi. Welcome to the Basics of Language and Speech Development. My name is Tiffany Munzer and I developed this in conjunction with my colleague, Dr. Ashley Dehudy. I'm so excited to share some information with you regarding how children develop language and speech. So to get started, what is language and what is speech? Language are the words that are used and how they're used to communicate and share ideas. Speech is the actual production of the words themselves. Both language and speech develop in the context of biology or nature, and then also the environmental input or nurture. There's a large body of literature on how children develop language and speech, but much is still unknown in regards to how children develop language and speech. I'd like to share with you what is known from the literature and some of the highlights in the research. So there's a large body of literature suggesting that there's some sort of biologic basis or infants have this natural inclination to learn language. So starting at birth, infants are programmed to learn language. Any and all languages with which they're exposed, infants are able to learn. They're able to distinguish different sounds of speech when playing a tape with speech forward but not backwards, suggesting that there's something special about speech itself that infants are especially attuned to. So infant's abilities start broad or more universal, then become more specific as they're exposed to different languages in their environment. It's important to note that the input of language occurs before the output of language. In other words, infants learn and understand language even before they're able to express the actual language itself. We call this receptive language learning which happens before expressive language learning. Interestingly, the ability to detect vowels at six months of age even before infants are really able to express language, actually predicts children's future language abilities at five years of age. So with more regarding the evidence of the biologic basis for a language learning, at six months of age, infants really have these universal abilities. They're able to distinguish differences in both English and non-English speech sounds if they're primarily exposed to English. However by 12 months of age, infants who are immersed in English only environments are not able to distinguish differences in non-English speech sounds. Which suggests some learning of the phonemes or the speech sounds that are particular to their language learning environment. Starting at 18 months of age, vocabulary increases rapidly, however, this seems less age restricted. For instance, adults who are learning new languages are more able to acquire new vocabulary, however, have a harder time learning the different speech sounds are the phonemes of that new language. By 18-36 months of age, toddlers began to organize words into sentences, and at 18 months of age most toddlers are able to start putting together two words into one sentence, and by 36 months of age we expect kids to be able to have three or more-word sentences. Though infants are programmed to learn language at birth, speech acquisition occurs later because of changes in the vocal tracts. So this really harkens back to our point that, the input of language really happens before the output of language. The ability to close and manipulate the vocal tract really occur starting at six months of age. Babbling or this consonant vowel over duplications like "bababa" or "dadada", start to occur around eight to nine months of age. The differentiation of language-specific patterns of babbling really starts around 10 months of age. So all of this evidence suggests that there's some sort of biologic basis or a neurologic basis for language learning. Why is that? The first three years of life are just an amazing time of rapid change in the brain. Within the first three years of life, and infant's brain actually doubles in size. There's so much neuroplasticity and synaptogenesis that's happening in the brain. The synaptogenesis is really this formation of connections between all of the different neurons. There's also a lot of pruning or weeding out of synapses that fire less and then strengthening of synapses that are fired more often. This is really what builds the architecture of what's important in that infants environment. So catching hearing loss early is so important because infants have so much neuroplasticity and they start learning language even at birth. There's a commitment of the neurocircuitry that's really dependent on the exposure to the environment. So it's really this nature plus nurture that facilitates language learning. So what is the environmental basis and what evidence do we have to suggest that infants learn with this environmental input as well? We know that early experience shapes language behavior, both the social interactions that are provided to an infant, and then also the cognitive processes of the infant themself. For instance, whether or not the infant is attending to some of this language in their environment. Children who are deprived of this language exposure after a critical window may never learn language. That critical window differs based on the type of language that researchers are evaluating. It's interesting to note that the first word spoken by infants are really driven by the people and the important things around them like their parents or pets, and then also social routines like hi or bye. So there's such a big environmental basis for language development and it really occurs in the context of a trusted and responsive caregiver. Social interaction is not just important for learning language, but it's a necessity. Adults provide this joint attention with an infant and are noticing the things that the infants are noticing in the environment and can point those out, and that's how infants learn best. Infants start to understand that language is used for communicative intent based on what the adults are doing in their environment and they have a strong desire to imitate. Infant's really are prime for this social interaction and a desire to imitate those around them. One study noted that, the mere presence of a human in a room with an infant allowed them to actually learn new syllables in a language versus hearing the same sounds on a television. They hypothesized that the infant's attention was actually better when a person is present. So this really drives home a point that screens are not a substitute for human interaction in learning language especially in infancy. That's why the American Academy of Pediatrics recommends limiting screen time in the early infancy years, just because it's hard for them to learn from a screen and they really are dependent on contingent adult responses in order to learn language. So that summarizes some of the highlights of research on how infants and children develop language. But what are some practical tips that we can support to encourage language development? Well, there's some evidence to suggest that if there are concerns about hearing, to complete an audiology evaluation, to make sure that infants are able to hear their environment. There's evidence to suggest that referring to speech therapy early on is important and will help kids make gains in language development. For parents, talking frequently and narrating what infants and young children are seeing in their environments can help promote their language development. Even going to the grocery store and pointing out things like green apples or purple grapes can help infants learn that vocabulary more readily and more easily. Then it's never too early to start reading to infants. So the take-home points of this lecture include that earlier is better because of the neuroplasticity happening in the first three years of life. Infants are really primed and wired for language. The input of language happens before the output of language, and language really happens in the context of social relationships and interactions. Lastly, if you have any concerns about speech, it's important to evaluate for hearing loss and refer for speech therapy early. Thank you so much for your time, I really appreciate it. If you're interested in reading more in depth of these studies, please feel free to refer to these references.
