Episode 23 - SLI vs DLD, misconceptions about SLI, early identification of SLI, and the genetics of SLI with Mabel Rice
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Mabel Rice, Ph.D., Director, Child Language Doctoral Program, The University of Kansas
Mabel Rice, Bio
For the Episode 23 Transcript, Click "Read More" below
00:12 Tiffany Hogan: Welcome to See Hear Speak podcast episode 23. In this episode, I talk with Mabel Rice, professor at the University of Kansas. Mabel shares key findings from her numerous longitudinal studies with children with specific language impairment, with discussions about misconceptions around language impairment, early identification of language impairment, and the genetics of language impairment. Thank you for listening! Don’t forget to check out www.seehearspeakpodcast.com, to sign for new episodes and content, read a transcript of this podcast, access articles and studies we discussed, and find more information about our guest. Speaking of these resources, I finally asked for some help, and now have a student assistant who is working with me to get the resources ready for each episode. One of my new years resolutions is to ask for help when I need it! Why is that so hard to do? Anyways, don’t forget, if you enjoy this podcast please don’t forget to subscribe and leave a positive rating on Apple Podcast, or wherever you are listening. Happy New Year!
01:20 Tiffany Hogan: Yeah. Well, welcome, Mabel Rice, to the See Hear Speak podcast, so excited to have you here today. I will start by having you introduce yourself.
01:33 Mabel Rice: Oh, I'm Mabel Rice. I'm a professor at the University of Kansas, where I have been on the faculty for a while now. I also direct a child language doctoral program, which is a cross-disciplinary doctoral program. I direct several funded projects, one of which is a training grant for doctoral students, a cross-disciplinary training grant. And I direct an Advanced Study Center on topics completely unrelated to what I'm going to be talking about here. So that's a little bit, that's a little bit.
02:08 TH: You're not busy at all, obviously [laughter]
02:12 MR: No.
02:13 TH: And I had the honor of being one of your trainees, even though Hugh Katz was my primary mentor, I was on your training-ship, and it was a real honor. And we still keep in touch because of that too.
02:25 MR: We do, and it's a very good group of people that have been part of our experiences, so. And of course, everybody is always a member of the family.
02:35 TH: That's right, it is an honor to be part of that elite group for sure. And we just have to say the rock chalk for sure.
02:42 MR: Right.
02:42 TH: So, I'm excited to have you on. Well, your whole career has been devoted to studying and helping children with Specific Language Impairment or SLI. And we've had a few episodes on the podcast to celebrate DLD Awareness Day. I think it'll be great for the listeners to understand the difference between SLI and Development Language Disorder.
03:00 MR: Sure, well, let me walk us into it. So the definition of Specific Language Impairment that I adhere to, is the one that the National Institute of Deafness and Communicative Disorders has posted on their website. They have a lovely new printed version of the information that's there that is available if you request that form of it. Anyway, Specific Language Impairment is a communication disorder that interferes with the development of language skills in children who have no hearing loss or intellectual disabilities. This condition can affect a child's speaking, listening, reading and writing. So notice that it's defined in ways that have inclusionary as well as exclusionary criteria. We can walk our way through how the history of this came to be later on. But it's been around for a long time. So SLI emerged in the 1960s, with work by Paula Menyuk at MIT, and has been studied certainly throughout these intervening years. Then we have another form of language impairment that I want to also queue up here, and it's called Non-Specific Language impairment. This includes children whose non-verbal IQ might be lower than what we would use in a classic definition of SLI.
04:37 MR: Because we never wanted to confuse entirely the children who had limited cognitive abilities in addition to language. This was in part because we were trying to figure out why do these kids have language impairments when they seem to have everything they need in order to get it going? So this Non-Specific Language Impairment, then includes children with borderline or below non-verbal cognitive abilities. And then we have, the more recent term, is Developmental Language Disorder, and that brings in a few other kids as well. So, this excludes the exclusionary criteria or more narrowly defined as a known biomedical ideology. But it makes a point of including risk factors, neurobiological or environmental risk factors. I have to say that SLI has never been defined by environmental risk in the classic way of defining that as low SES. There is another kind of environmental risk, like exposure to toxins, for example. But in this literature, environmental risk has been interpreted to mean families who are poor, who have few resources, and mothers who have limited education, those children have never been excluded from the diagnosis of SLI.
06:10 MR: And in fact, we studied that issue very carefully in order to understand it better. So now we have, back to Developmental Language Disorders. It’s more inclusive and it does include ADHD, which gets handled on more of an ad-hoc basis across different people doing research on SLI. It does not require a mismatch between verbal and non-verbal ability, neither does SLI. Those are debates that are playing out in other places in the world more than they are here in the States now. So it hasn't been there. But I have to say, that one of the issues with this new terminology is it's actually old terminology. And in the US, it has a long history and still current publications in which it means something different. It would include children who have autism and fragile x and epilepsy and cerebral palsy as being children who have Developmental Language Disorders that are running with other conditions in the same youngster, at the same time. So that's...
07:22 TH: That is really important to know, especially when you're thinking about listeners and new doc students and clinicians and going into the literature and pulling these two groups out. And trying to figure out how they fit to their clinical practice. It's so critical that they look at the inclusionary criteria. And sometimes it's maybe not as clear in the articles, but we hope it is. And I like how in the forthcoming prospectus paper, you frame the difference between SLI and DLD using an analogy of precision medicine, which is such a big topic now and so important. And I'd love for you tell the listeners more about that analogy, and how you see the of label Specific Language Impairment fitting into the current advocacy for children with Developmental Language Disorder with this precision medicine in mind?
08:09 MR: The example that I gave from precision medicine is breast cancer, which is certainly a form of medical treatment and a medical condition that we're quite familiar with. And I think it's informative for us to think because breast cancer goes... Often goes undetected, as does certainly SLI in many cases, so however we're defining DLD and even NLI. So the medical community has put in place an extensive screening program for identifying breast cancer. The mammograms are out there, women are encouraged to receive mammograms, even though the rate of breast cancer in women overall across all ages is about 10%. And that's interesting because we estimate the rate of these children that we're talking about here as between 7 and 10%. So massive mammogram screening protocols and encouragement are in place. It meets all the insurance requirements and everything, and that can pick up breast cancer that can't be detected in any other way. Because diagnosis is at the heart of medical practice.
09:31 MR: Diagnosis is also at the heart of good speech pathology practice, I believe, and at the heart of good teaching practices at large. We have to understand what we're dealing with. Once the mammogram comes back with a positive response on the screen, that's only the beginning of what is needed for planning a program of treatment or intervention in our case. The treatment of protocols then, for precision medicine treatment of breast cancer, want to know what kind of a growth is this? How large is this growth? What is the prognosis for a successful treatment depending upon which elements of treatment? And what treatment do we begin with? And then what comes next? And how often do we follow up? And do we really need the third element of a treatment? All of those are regarded as essential at the beginning, at the outset information for working with. I think that this can be a comparison point for us that, first of all, most of these youngsters that we're talking about are unidentified for different reasons.
10:50 MR: If we had screening programs for when these kids are younger, around early years of school or even late preschool, it would be fantastic. We would want to know, what do we need to know about their speech and language? We'd certainly want to know, do they have language problems even though they don't have speech problems? We know from very good research findings, that most of these kids do not have speech problems, so you can't pick them up on that obvious basis. You have to do more probing. You have to find out how good is their vocabulary? And how good are they at formulating sentences? And to what extent do they really understand all of the grammatical elements? And how long does it take them to figure this out? Are they running much, much older than the children typically do?
11:43 MR: Then we have to figure out which ways of intervening do we have? Can we work with the families to change some elements that's within their daily activities at home? Do we need particular kind of focused practice sessions? Do we need to work with the teachers on how to adjust their reading curriculum? All of those things require precision in the same way that identification and treatment of breast cancer is needed. I think that we have defaulted a little bit in thinking that maybe we don't have to bother with that initial information gathering part. But in fact, just like our treatment for breast cancer, we really would want to have that information in hand.
12:34 TH: Oh, I definitely resonate with you on this early identification. Suzanne Adlof and I recently published a paper arguing for screening of language impairment, screening for language within the current school system because as you know there's all these laws about screening for dyslexia, I think if we could capitalize on the culture of screening, to add in screening for language impairment, that would be ideal for all the reasons you mentioned. We really drew on your seminal work in that paper to say that you can identify a SLI early. So I'm wondering if you could tell us a little bit about your findings related to the grammatical deficits of SLI, the optional infinitive hypothesis, and what are the implications for SLI? And also early identification of SLI? Because we're talking about early identification here.
13:31 MR: Yeah, well first of all, let me say with regard to the work you're doing with Suzanne, the sound that you hear from here is the sound of my hands clapping. I mean, I think this is fantastic! You guys are really leading the way in advocating for this and collecting the valuable information and detail and data on how this matters.
13:50 TH: Oh, thank you. Standing on the shoulders of giants.
13:54 MR: Well...
13:55 TH: Honestly.
13:57 MR: I think what you're referring to is this work that I've done on a... What became known as a grammar marker.
14:04 TH: Yes.
14:05 MR: Just like there's markers for various kinds of breast cancer, this is one marker that we worked on, and it had several things that made it seem to be possibly useful. Let me say at the outset, I don't believe it's the only possible marker. I believe there's other markers in both speech and language and in other elements of youngsters' communication conceivably. But it's hard to find them, because one of the things that's good to have for a potential marker is something that almost every child that doesn't have a language impairment knows how to do this.
14:42 MR: It's highly likely that the child who has a language impairment does not know how to do this. So the work was informed by theoretical linguistics and what we know about how the adult grammar works. And people back just a little before 2000, were very interested in why it took English-speaking children so long to learn some parts of the adult grammar. Yet, other children, Spanish-speaking and French-speaking children, learned these comparative parts pretty easily. So it was a question of interest to linguists wanting to know what is it about the languages that made it easier for kids in one than in the other? So when I started studying this during leave time that I had at MIT and at Harvard, I was struck by the fact that this was first of all, a place where children... These forms were required in their grammar. So you could ask children to say things, and notice if they omitted parts of it. So it set it up as, "Wow, they can do these things, but the children with language impairments cannot do those like the other children."
15:56 MR: So we had identified some parts of the English grammar that we are able to characterize as being required in the adult grammar, and therefore we can measure. Our measurement of how the good children are learning the system is indexed to the standard for the adult grammar. That's the only thing that we have right now that's really progressed towards the adult grammar in the way of measurement. It has to do with little forms that mark past tense and present tense, and mark subject-verb agreement, and it's in the little parts of the grammar that families never teach to their children. Almost all children just learn this by listening and picking it up without explicit instruction.
16:45 MR: So it has to do with the difference between, "Yesterday, I walk to the store," or "Yesterday, I run home," when it should've been, "Yesterday, I ran home." In English, we're required to say, "She likes cookies," and, "She like cookies," isn't good enough or, "She like apple," isn't good enough, because that little S is there just to flag that the subject is a single person. Those ways of measuring things then led to ways of comparing performance relative to typically developing children at the same age. And now we have very good sets of normative data on it, and we can make very good estimates of how far a child is from what's expected. In fact, if I can put a little additional note in, we have on the Apple store for free, an app that actually does this in ways that children like to play with the format. They don't have to say anything at all. Within 10 to 15 minutes, you get a pretty good idea of how this child is mastering this relative to other children of the same age.
18:08 TH: That was my next question, was to have you tell me more about that app. What's that called? We will definitely link it to the resources. And also, can you tell us about your thinking with using computer testing versus in-person?
18:20 MR: Sure. The app is called Grammaggio. G-R-A-M-M-A-G-G-I-O. It is available at the Apple store. So if you get into the Apple store and look for it, you'll find it, you click on it, you can download it. It runs on an iPod or on an iPhone. And either one of them, in 10 to 15 minutes, a youngster hears a voice saying sentences and the job is to say yes, if the sentence is correctly formed, and no, if it isn't. Or because in Kansas, the little girls don't like to say, "No", they prefer to say, "Not so good." So either way it works. And we do have practice materials that we'll be putting up within the next few months, I would imagine.
19:18 TH: Oh, awesome.
19:20 MR: Yeah. So it's now available! It's in use around the world, and it's being used in a number of research studies as well, which we encourage very much. I have to say, it was funded by the National Institute of Health.
19:32 TH: That's great.
19:34 MR: So they're very interested in developing these things.
19:36 TH: That's great. And then, what was the reason for computer testing, then? What are some of the benefits that you see?
19:44 MR: You don't need a trained adult to do it, and you don't have to get an adult trained to do it close to the child. Those are the big expenses in the kind of research that we do. Each of us have labs that require us to train people to do this, so that it's likely that the information will be collected in the same way. We don't want to confuse differences in children with differences in examiners. So that can be very expensive. It's always been an issue in the schools because time is an issue in the schools. Sometimes, it can take 20 or 30 minutes or much longer to get this information from a child. Teachers don't have that time, speech pathologists don't have that time.
20:28 MR: So under these methods, it's possible to build it in a way that children will attend very carefully to each sentence they hear, and just push a button, and keep going. If you present it in a way that holds their interest, then it takes a minimum of time, there's no calculation involved, you don't have to train people on how to score it. It provides a score, and it also provides a statement of how a child's performance is relative to age expectations. So in a small investment of time and energy, you can get a lot of information out of it. So it's not the full diagnostic set of information that's needed. It's not intended to be that. It's intended to be the equivalent of the mammogram. It's a way to get a quick snapshot in that happens to have good statistical properties for helping us try to go further.
21:36 TH: Yeah, that makes a lot of sense. And I know what I learned about screening and sensitivity, specificity, false positives, I learned in your doctoral seminar. It's really an awesome experience to get to see some of the early work you were doing. And now to see it in app form is really amazing. It really got me thinking too, about the grammatical marker and how that's such a... It's so powerful, I think. As you've taught me, and I've read more about too, it's just this kind of impoverished stimulus. You don't need much exposure, which is different in the vocabulary, for instance, right?
22:07 MR: Mm-hmm.
22:08 TH: So vocabulary...
22:08 MR: Exactly.
22:10 TH: You give those measures, you can get a lot of false positives because maybe the child wasn't exposed to it. As opposed to grammatical markers, it takes very little exposure.
22:18 MR: Well, and that's in fact very interesting. The other way too to look at it is that young children hear these forms all the time.
22:31 TH: That's true.
22:33 MR: They're very frequent in what children hear. Adults must use these forms for every well-formed sentence. And particularly, questions are very informative in this, and children hear questions all the time. The interesting thing is that typically developing kids just learn this. I mean, no one ever sits down and lays out the grammatical rules. They just pick it up on their own. But these guys who have specific language impairment and other forms of language impairment, really struggled with this particular part of the grammar.
23:09 TH: So you've studied children with Specific Language Impairment longitudinally, which you taught me, and I've had great experience myself working longitudinally. So you can see how children really develop over time. And I think in doing so, you have such unique insights into their change over time, and how SLI impacts a person across their lifespan. So I was wondering what you could tell us about some of your key observations about SLI over time, from early childhood to adulthood. What have you seen as the way persons can support those with SLI to live their best lives? Listeners might be wondering, what does SLI look like across time?
23:46 MR: I'm happy to do that. I also want to make it clear that our longitudinal study is based on children that we recruited into this study because we started at the beginning wanting to get children with SLI and compare them with typically developing kids. Later on, we were very interested in finding families of equivalent socio economic status as a comparison group as well. As we were working with the children, we realized that there was something happening in the families, so we began to recruit the siblings and the mothers and fathers. Until now, it's family based. And we have, we certainly have children that were identified at the outset with SLI. Usually because they were known to somebody, usually the speech pathologist had picked them up somehow. But when we were looking at the siblings, then we have most of our kids with SLI in our sample have never been identified by a practicing speech pathologist or anyone else in their communities. That gives us a good idea of what's happening in the usual case where they're unidentified.
25:02 MR: Our children attend school in this sample in the Midwest. We have something like 125, 130 different attendance centers, so their schooling experiences are very different. However, the presentation of their language symptoms is very similar from one child of this kind to another one, regardless of what school setting they're in. Now we also know quite a bit about their mothers and fathers and other members of their families, some families we have many cousins, and extended family members. So from all of this, we have learned that children with SLI are likely to start language acquisition later than expected for their age. So they just don't get started as early as other kids. Within the same family, there will be kids who start on time and go great, and then there will be a child in that family who cannot.
26:02 MR: We have some families that literally have the ability to have the resources to buy anything they need or want. One of the things they want most of all is for this little boy to be like his brothers and everyone else in the family who always found language to be very easy. So we have those kinds of circumstances. So yes, one of the hallmark characteristics is a late start. And late start means that if something isn't up and running pretty well, certainly by three years of age, and even by two years of age, it's time for someone to begin to wonder. Do we need more information is needed to really start in on a screening and a diagnostic process? The interesting thing is that we've documented a great length across many different ways of measuring speech and language. Once these youngsters get going, they change at the same rate. So the speed at which they change is the same speed as their age peers, just offset by about two years. When they begin to level off, they all begin to level off around 10 years of age, 8-10 years of age. That’ss where pre-adolescence begins in our children in today's world.
27:31 MR: So what happens is, they get into middle elementary school, and everybody's not as fast in learning language as they used to be. And these guys level off then too, which means that they're left at a level still hanging below those of other children. We've documented this very thoroughly for both grammar and vocabulary. So it leaves us with this, "What on earth allows them to learn so quickly once they get going, but not learn fast enough to close that gap?" It's one of the things that we don't understand about language acquisition in children. It also has to do with what happens to these guys as they become young adults. And we know that they're more likely to go into employment when they finish high school.
28:27 MR: So here's the kids who have the most difficulty with language that are going into the job market. And the children who have the best language, paradoxically enough, go into educational situations beyond high school. They continue to get extensive help from the adults and their family and everybody else in society to help them get through college. Then the youngster with SLI often is graduating into an employment situation and has to figure it out. We've come to know these families quite well. We know that the mothers and fathers, it's not unusual at all, that one of them or maybe even both of them had a similar history as a child. And more than anything they want their youngsters to have this gift of being able to talk well in sentences, and to negotiate disputes, and to be able to present themselves well in a job interview. All of that is dependent upon language that isn't very easy for them.
29:37 TH: And how does that play out in what you've seen with parents who are dealing through an IEP process? Or dealing with advocating for their children in the schools?
29:49 MR: The interesting thing, and we learned this from the families. The families have told us that one of their worst experiences is having to go to school for an IEP meeting and meeting with the teachers. This is because for one thing, it brings back in their memories all the times that someone told them they just weren't trying hard enough. If they only applied themselves more, or if their mother or father were only more encouraging, they would do better. So they have a sense of shame. They have a sense of recall of frustration when they were a child, and which they still have in how to manage things in the world. Then they're in a meeting where a whole team of people is looking at them, and telling them what their youngster's limitations are. What they hear is, "That's what my teachers said about me when I was a child."
30:48 MR: More than a few of these families will have one or both parents who aren't very strong readers themselves. Then they will be told that what you have to do is read more to your child, and reading was never easy for them. It isn't the kind of activity that is comfortable and encouraging and all of that. It's associated with this sense of shame, the sense of not being as good as they should've been, and this sense that it's their fault. So all of that gets in there and it's very, very hard for the people on the team to pick that up. Because these are folks who are very conscious of trying to maintain their dignity, and one way they do it is that they just don't talk a lot in those kinds of circumstances.
31:41 TH: Absolutely. And I think you bring up all these different misconceptions about SLI, and I think that your work has really tried to lay rest some of these misconceptions. I wish that all of our listeners could really think deeply about the misconceptions they might have. Let’s talk about a few of those misperceptions. So one you brought up was, if they could just try harder. So what has your work shown about, and your work with families, about this misperception that kids just need to try harder?
32:16 MR: Well, trying harder is prejudicial. Typically developing kids don't try at all.
32:25 TH: Exactly.
32:27 MR: They didn't get to their advantage because they applied themselves, they don't know how to explain the rules of the grammar and all of these vocabulary items that they know either. So it's really prejudicial toward the low functioning, the low achieving guys. They're not low achieving in everything, that's the interesting thing about them. They're very socially motivated, they want to be the popular kids. We've actually run a questionnaire on our sample here for quite some time, in which we asked them things like, "Are you a good student?" This is for children in junior high, middle school, and high school. "Are you a good student?" and they say, "No." And then we ask them, "Are you very popular with your peers? Do you have many friends?" And the answer is likely to be no or not so much. And then we ask them, "Does your teacher think you're a really good student?" And the answer is no. And then we ask them, "Do you like to go to school?" And the answer is yes.
33:47 TH: Wow.
33:48 MR: Almost all of the children that we have studied, graduate from high school, they stay in school. They want to be with the other kids. They want to be part of the social hangout groups, and they want to be like everybody else. This is something that becomes an important part of their sense of personal dignity, and their sense of personal affiliativeness. They're very affiliative, they want to be part of a team. When they do enter into the workforce, they're really keen to be a good worker, and get along well with their fellow employees. So the assumption that they just weren't trying hard enough, it isn't a motivational breakdown here. It's something more interesting than that. The motivational breakdown doesn't take into account that within the same family, you will have children who have very strong language and children who really struggle with it. The other thing is that they're not very good at winning arguments, because they can't control quickly how to reframe their sentences to get another approach on the problem.
35:06 TH: Yes. So that negotiation argument kind of just expressing your side of a story and your views on the world, it's so difficult.
35:18 MR: Yes. Yes, it is. And the other misconception that I often hear is these kids just aren't very smart.
35:26 TH: Yes.
35:29 MR: And that's just not true. When we measure them with tasks that get at what they know, without having to test their language. So there's a number of ways to test what's called non-verbal cognitive abilities. It has to do with solving mazes, finding similarities from one picture to another one, forming designs with blocks. There's a number of classic psychological methods for doing this. And under those methods, we know that we certainly have a surprising number of individuals who have very high non-verbal IQs, and still have these grammar problems, and really struggle with their language. So that's just not true to fact. That's just not the way it works. Interestingly enough, it can go the other way, you can have individuals with very low non-verbal IQ, who have fantastic language. Some of these individuals have been studied in great detail because it's been absolutely fascinating, how these things can be distinct from each other.
36:43 TH: Yeah, that plays out also in dyslexia too, so they relate to the word reading, right? It's just been this big debate, and we just don't see that it's related to intelligence. But it is the forward-facing, unfortunately, first formative experience that these children have: communicating with language, learning language, learning how to read words in a formal setting. Then that start, unfortunately, because it is the forward-facing ability, the measurable ability that their teachers see and their parents, starts to form, their self-esteem and how they perceive themselves as students, how others perceive them as students. The other misperception I hear a lot is that only children who live in poverty have a language impairment.
37:29 MR: That one, I feel very strongly about, and it's not true either. Some of the most heart-breaking stories have been from families with unlimited means, and it does not allow them to buy the resources to enhance their child's performance on this. It's just another way of adding to the shame and the frustrations that go with this. It is also true, as I was saying, that if there is someone in the family with a similar history of this, then it is more likely that they will not have finished a college degree. So the extent to which an advanced degree is supporting increased financial resources, that becomes an issue for the families. It is not the case that poverty causes this. Within the same poor family, there are children with high verbal skills, and there are children of the sort that we're talking about now. It makes it very clear that it's not poverty. Even sometimes it's said that the mother didn't talk to her child often and enough. That's not the explanation, either. It's interesting that there's a great variation around the world, in which people believe that it's even a worthwhile thing to be doing, to talk to your children, because what do they know?
39:18 TH: Absolutely.
39:19 MR: And in our culture, it's considered charming and sensitive to ask your child a bunch of questions to which you know the answer. What color is this?
39:27 TH: Absolutely.
39:30 MR: And many cultures think that's just the weirdest thing ever. Why would you ask the child a question that you know the answer to?
39:38 TH: Absolutely, absolutely. I work with the Data Reservation, it's see and not be heard. I had a Fullbright scholar from Finland, she happened to come last year during Halloween, in my small town I live in. We shut down the whole downtown for the children to trick-or-treat. And she was just blown away by this because she's like, "We cherish our children, but we would never shut down a city to do this. This is like really baffling," and it is true. It's such a kind of a Eurocentric view, I think.
40:10 MR: It is. It is.
40:10 TH: And maybe even more American, but I don't know, to have this kind of focus. We know children in multiple cultures, they show these variations in language ability. It is unrelated to what they're hearing from their parents and how much they're asked a specific question for instance.
40:26 MR: It is. It's the same sort of thing that thinks Chinese is a very complicated language, but English is a very easy language.
40:33 TH: You're right.
40:37 MR: That's not agreed upon either.
40:39 TH: Not at all though. No, that's so true. I think it's interesting to me how... And I'm hoping that SLI will follow in the wake of this. I do think there's become more and more understanding that, for instance, autism isn't caused by poverty. Autism or even dyslexia, I think, there's a lot of movement towards that.
41:00 MR: Exactly. Exactly.
41:00 TH: I think that movement, I'm hoping, that we're riding in the wake of that too based on the work you've done. We can get the word out about these children as well. When I give talks, I always try to make some of those comparisons because it does seem like people understand those a bit more, even though they don't understand that the prevalence is slower and the prevalence is so much higher for SLI. So, you’ve talked a bit about your family studies and I just wanted you to talk too a little bit about your twin studies and what you've found with genetics. And it seems like all of this is concluding that this is a neurobiological difference that a child is born with, but tell us about your genetic studies and some of the findings.
41:44 MR: Well, there's two branches of it. Let me start with the twins because the logic of the twin study is interesting. When you have two children that were conceived at the same time, and in the uterus at the same time and born on the same day, it's interesting that in humans, they come in two different kinds of pairs. One kind of a pair are known as identical twins or in literature, monozygotic, meaning that they started as one fertilized egg. Then it split into two zygotes, two very beginning forms of human beings. And so, their DNA was at first thought to be completely identical, but we now know that there's some little tiny variations in it. These are of interest for people that study this in greater detail. But for us, we can think of them as identical, so they have the same DNA. So, that means that the extent to which language is inherited by virtue of what's in the DNA, they should be very much like each other in their language. And their comparison is with pairs of children that are not identical twins, they are fraternal twins. Fraternal, meaning, family-like basically.
43:21 MR: They're no more like each other than other siblings. The DNA is different. There were two fertilized eggs that were conceived at the same time. They were carried in the uterus at the same time. So, with fraternal twins, you can have a boy and a girl for example. With identical twins, they are always of the same sex. This means that the logic for doing comparisons within the twin pair is that the twins who are MZs should be more like each other in language than the twins who are DZs, or fraternal twins, should be less like each other. They should be no more like each other than brothers and sisters in the same family. Because they're born at the same time, any kind of environmental influences, like whether or not there's lead in the water supply or anything like that, would be the same for those children growing up. So, under those circumstances, we can run all kinds of wonderful statistical models now asking these questions, and we can ask about different dimensions of speech and language. Out of it comes a heritability or an estimate of the extent to which these traits that we're measuring are inherited. And we're finding very clear evidence that there certainly is something that is inherited.
44:52 MR: Our studies are aligning with some earlier studies suggesting that the evidence for inherited contributions increases with age. It's high for speech until almost all children have figured out their speech system, unless they're neurologically impaired certainly by the time they're six or seven. So we don't hear much about heritability of speech beyond that, because everybody has the same speech or you can't communicate at all. But the language piece continues to be of interest, and we know that grammar, this grammar marker we're measuring consistently yields some of the highest heritabilities of what we're measuring. But vocabulary is heritable as well, and other things that we're measuring in the details of the system. So to go back to precision medicine, as far as we can follow that model, the more precise we get, the more we find evidence of heritability. It's in there in different dimensions. We know the most about this one part of the grammar to look at. Now, it turns out there's also a twinning effect, such that twins are later in learning language. And we can see that because it's true for both MZs and DZs, but we can also see that it's more evident for identical twins than it is for fraternal twins. There's huge implications for that in artificial reproductive methods.
46:31 MR: Some of the other ways in which our whole understanding of reproduction in humans has really changed greatly recently. But this is an interesting line of work. It was made possible by colleagues, people who became my colleagues who contacted me a long time ago and said, "Would you come talk to us? We have the means to do a twin study but we want to talk to you about whether or not you would lead such an effort." And it turned out that that was possible. And so, our twin data collection was done in Australia because we could get the medical records there that are not possible to do it that way in the US. That's now running in parallel with the family-based pedigree studies that we're doing in the US. That’s at the level of Molecular Genetics, where we're actually looking at different levels of gene expression. And our lab is one of maybe four or five around the world that are really involved in doing this work. It's tedious work. It has been frustrating because there had been some discoveries and some leads. But it is turning out to be a challenge to replicate across different groups, and to replicate the same findings in ways that would make us all confident that we really have discovered a part of it. So most of us do believe that ultimately it's got to be something in the neuro-biology, that's under gene control systems of various kinds. But we don't have any of those pathways well identified yet, although many people are looking.
48:20 TH: That's fantastic, and it's such a big contribution to know that we can say definitively that it is a neurobiological difference and it's not caused by parents, they don't need to feel guilty. Although, I do know that it can make them feel guilty at times thinking they passed it on, but there is a variation that occurs. So, it's not inherent that you're definitely passing it on and obviously, it's not inherent that you have to have a parent that has SLI to have a child with SLI. So, those variations exist.
48:53 MR: Going back to the breast cancer comparison, we may in fact find something similar. We now understand that there certainly are cases of breast cancer that have a genetic origin. But the large number of breast cancers are not of that type. So, they’re further ahead than we are. But of course, you know this from your work on dyslexia as well, that the work on inheritance in dyslexia is ahead of the work on speech and language, language in particular. The families can find comfort in knowing that there's an inherited component, but it also is a little unnerving to wonder where did this come from within the family. And now is a good time to point out that you can have a genetic causal pathway that's not inherited, that's not passed down through families. So you can have gene effects that aren't running in families. So these are all part of the complications of what we now know about this.
50:11 TH: Absolutely. Well, thank you for telling us more about that work. And we have a lot of listeners in Australia so they'll be interested to hear.
50:20 MR: Great.
50:21 TH: You've got some work there too. So I'm mindful of our time and I want to make sure...
50:24 MR: Let me give a shout out to Steve Zubrick and Kate Taylor, who had been my colleagues and partners and we're still working on producing the papers, and so I'm still in regular touch with them. They're part and parcel of what I'm talking about of that twin study.
50:44 TH: That's great, and I'm sure some of the listeners will recognize their name. And they're in Perth, is that correct?
50:49 MR: Yes, Kate is now based in Tasmania. But they both have a connection in Perth. Steve is still in Perth at the Telethon Institute there.
51:02 TH: Oh, great. Well, being mindful of our time, I wanna make sure I ask you the two questions I always ask every guest.
51:09 MR: Yes, why not?
51:10 TH: The first one is, yes, what are you working on now that you're most excited about?
51:15 MR: Well, there's a couple things. One is something that I can't talk too much about but I'm quite excited about it. So here it is.
51:22 TH: Tell us a little bit.
51:24 MR: It is work that's in collaboration with a company that does work on reading instruction in the schools. So, this whole electronic presentation systems of reading, which of course is related to language, and we'll see how that proceeds.
51:47 TH: I'll be watching you.
51:50 MR: Yeah, I am very interested in the emerging world of electronically mediated systems of teaching and identifying children who are not performing as well as we would expect them and want them to. So, it goes back to the analog, again, on mammograms and how we might get better options for quick and easy screening materials in this way into the system. It requires a very different kind of information and data collection and all of that stuff.
52:35 TH: Absolutely. And what is your favorite book from childhood or now?
52:41 MR: I read this too, and I recently saw the movie Black Beauty again. God, I had that book read to me when I was a child. I think I was in second grade when I had measles or chicken pox, something that was the scourge of the year at that time. I really enjoyed that one immensely. But I'm a very avid reader. I always have been. So I read voraciously. I read mysteries and what, suspense novels of various kinds. I'm an avid movie goer too.
53:24 TH: Oh, me too. Me too.
53:26 MR: Very keen on the movies.
53:29 TH: Oh, that's great. I love when... You know my favorite is... Maybe you feel this way too as a book reader and a movie goer, I love when I can read a book and go to the movie to see the movie I was reading...
53:39 MR: Oh yeah. Yes, yes. Well, then of course...
53:40 TH: Because then you can see how they envisioned it, right?
53:43 MR: Well, this weekend is the opening of the movie version of Cats.
53:47 TH: Yes.
53:47 MR: So, I will be there on Friday night to check it all out.
53:52 TH: That's exciting. I will be also attending a big premiere of Star Wars. Awesome. [chuckle]
53:57 MR: Oh yes. Yes, yes, I know. Well, that's second on my list.
54:02 TH: That's right. Yes, yes, yes. Yes. Well, having a teenager...
54:03 TH: Having boys and having a teenager... I thought about that in October or something, so...
54:11 MR: Yes, indeed. Indeed.
54:13 TH: Well, I hope to see Cats as well. I would love that. Well, Mabel, thank you so much for spending your time chatting with me today and sharing your findings with the listeners. I very much appreciate it.
54:22 MR: Oh, it's been my great pleasure. And Tiffany, I just have to tip my hat and along with everybody else for your willingness to take on podcasting as your hobby.
54:33 TH: Well, it's a little crazy, but I have to say I absolutely love it. If you're gonna have a hobby, why not have one that maybe entertains someone out there, so... [chuckle] And brings information out. It's such an honor to shine a light on the people that have so generously trained me, like yourself and others. So, thank you again. Thank you.
55:00 MR: Well, it's my great pleasure and have a good holiday.
55:03 TH: You too!
55:06 Tiffany Hogan: Check out www.seehearspeakpodcast.com for helpful resources associated with this podcast including, for example, the podcast transcript, research articles, & speakers bios. You can also sign up for email alerts on the website or subscribe to the podcast on apple podcasts or any other listening platform, so you will be the first to hear about new episodes.
Thank you for listening and good luck to you, making the world a better place by helping one child at a time.