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Canonical Babbling Trajectories across the First Year of Life in Autism and Typical Development

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Title: Canonical Babbling Trajectories across the First Year of Life in Autism and Typical Development
Language: English
Authors: Helen L. Long (ORCID 0000-0001-6406-1222), Gordon Ramsay, Edina R. Bene, Pumpki Lei Su (ORCID 0000-0002-9392-360X), Hyunjoo Yoo, Cheryl Klaiman, Stormi L. Pulver, Shana Richardson, Moira L. Pileggi, Natalie Brane, D. Kimbrough Oller
Source: Autism: The International Journal of Research and Practice. 2024 28(12):3078-3091.
Availability: SAGE Publications. 2455 Teller Road, Thousand Oaks, CA 91320. Tel: 800-818-7243; Tel: 805-499-9774; Fax: 800-583-2665; e-mail: journals@sagepub.com; Web site: https://sagepub.com
Peer Reviewed: Y
Page Count: 14
Publication Date: 2024
Sponsoring Agency: Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) (DHHS/NIH)
National Center for Advancing Translational Sciences (NCATS) (DHHS/NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD) (DHHS/NIH)
National Institute of Mental Health (NIMH) (DHHS/NIH)
Contract Number: T32HD007489
U54HD090256
TL1TR002375
UL1TR002373
R01DC015108
P50MH100029
Document Type: Journal Articles
Reports - Research
Descriptors: Infants, Infant Behavior, Child Language, Oral Language, Autism Spectrum Disorders, Child Development, Symptoms (Individual Disorders), Syllables, Gender Differences, Coding, Interrater Reliability, Socioeconomic Status
DOI: 10.1177/13623613241253908
ISSN: 1362-3613
1461-7005
Abstract: This study explores vocal development as an early marker of autism, focusing on canonical babbling rate and onset, typically established by 7 months. Previous reports suggested delayed or reduced canonical babbling in infants later diagnosed with autism, but the story may be complicated. We present a prospective study on 44 infants later diagnosed with autism spectrum disorder compared with 127 infants later identified as typically developing who were followed longitudinally with day-long recordings from 0 to 13 months. Eight 5-min segments from each of their recordings were coded for canonical and noncanonical syllables. The results confirmed many reports that canonical babbling is a robust feature of human vocal development in the first year of life, with small overall mean differences in canonical babbling rates between the autism spectrum disorder and typically developing groups beginning around 9 months, primarily in males. Our findings highlight the importance of considering sex differences in vocal communication as part of the early detection and diagnosis of autism when determining the need for communication supports to maximize outcomes.
Abstractor: As Provided
Notes: https://osf.io/zea63
Entry Date: 2024
Accession Number: EJ1450083
Database: ERIC
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  Value: <anid>AN0180988103;f9d01dec.24;2024Nov22.02:17;v2.2.500</anid> <title id="AN0180988103-1">Canonical babbling trajectories across the first year of life in autism and typical development </title> <p>This study explores vocal development as an early marker of autism, focusing on canonical babbling rate and onset, typically established by 7 months. Previous reports suggested delayed or reduced canonical babbling in infants later diagnosed with autism, but the story may be complicated. We present a prospective study on 44 infants later diagnosed with autism spectrum disorder compared with 127 infants later identified as typically developing who were followed longitudinally with day-long recordings from 0 to 13 months. Eight 5-min segments from each of their recordings were coded for canonical and noncanonical syllables. The results confirmed many reports that canonical babbling is a robust feature of human vocal development in the first year of life, with small overall mean differences in canonical babbling rates between the autism spectrum disorder and typically developing groups beginning around 9 months, primarily in males. Our findings highlight the importance of considering sex differences in vocal communication as part of the early detection and diagnosis of autism when determining the need for communication supports to maximize outcomes. Our study examined how babies develop their ability to talk to help identify early signs of autism. We looked at babies' production of babbling with mature syllables across the first year of life. Babies usually start producing mature babbling at 7 months of age before they say their first words. Some studies have suggested that babies who are later diagnosed with autism produce this kind of babbling less frequently in their first year of life, but other studies have shown complicated outcomes. In this new study, we followed 44 autistic babies and compared them to 127 typically developing babies. We recorded the babies once every month, all day long, from the time that they were born until they were around 13 months old. Then, we studied their mature babbling from segments of these recordings. We found that the rate at which babies used mature babbling was lower in boys with autism, and higher in girls with autism, compared to babies without autism. This research helps us understand how babies with autism learn to talk. It also raises important questions about differences between boys and girls with autism. Our study can help us improve how scientists and clinicians can identify autism earlier, which could lead to better communication supports for autistic children and their families.</p> <p>Keywords: autism spectrum disorders; canonical babbling; communication and language; early detection; vocal development</p> <p>Prior work has established a clear link between prelinguistic vocal development and the emergence of language. Stage models show systematic progression of speech-like vocalizations across the first year ([<reflink idref="bib25" id="ref1">25</reflink>]; [<reflink idref="bib63" id="ref2">63</reflink>]), starting with vowel-like sounds ("vocants"), squeals, growls, and raspberries in the first half year and culminating in frequent production of canonical babbling (CB)—utterances with sequences of consonant- and vowel-like sounds such as "baba," "nana"—in the second half year ([<reflink idref="bib26" id="ref3">26</reflink>]; [<reflink idref="bib42" id="ref4">42</reflink>]). After the onset of repetitive CB, usually around 7 months, additional months pass before first words appear ([<reflink idref="bib49" id="ref5">49</reflink>]), even though canonical syllables have the acoustic properties necessary to serve as words as soon as they begin to be produced by infants consistently ([<reflink idref="bib52" id="ref6">52</reflink>]).</p> <p>A central goal in seeking early markers of language disorders is to find early vocal predictors of delays and differences relative to expectations for typical development. Numerous reports have suggested it may be possible to predict later language impairments by studying infant prelinguistic vocalizations, especially after the canonical stage has begun ([<reflink idref="bib28" id="ref7">28</reflink>]; [<reflink idref="bib40" id="ref8">40</reflink>]; [<reflink idref="bib46" id="ref9">46</reflink>]; [<reflink idref="bib64" id="ref10">64</reflink>], [<reflink idref="bib65" id="ref11">65</reflink>]). Yet, both early precanonical vocalization and CB have been found to be quite robust across a variety of factors that were previously thought to potentially predict slow development. Infants in bilingual homes, for example, show no signs of having delayed CB ([<reflink idref="bib44" id="ref12">44</reflink>]).</p> <p>CB occurs in infants with a very wide variety of prognoses with regard to communication development, but even so, the onset and/or rate of CB have been reported to be delayed in some clinical populations. The most salient of these are bilateral congenital deafness ([<reflink idref="bib6" id="ref13">6</reflink>]; [<reflink idref="bib68" id="ref14">68</reflink>]; [<reflink idref="bib70" id="ref15">70</reflink>]) and Williams syndrome ([<reflink idref="bib39" id="ref16">39</reflink>]), where the onset of CB can be delayed by many months beyond expectations for typically developing (TD) infants. But other conditions appear to show only minimal delays, for example, Down syndrome ([<reflink idref="bib37" id="ref17">37</reflink>]), cleft palate ([<reflink idref="bib4" id="ref18">4</reflink>]), fragile X syndrome ([<reflink idref="bib2" id="ref19">2</reflink>]), and tuberous sclerosis ([<reflink idref="bib12" id="ref20">12</reflink>]).</p> <p>Research on CB in infants later demonstrating autistic characteristics and diagnosed with autism spectrum disorder (hereafter interchangeably autistic infants or "ASD" infants) has revealed mixed evidence on the presence or absence of delays in the onset of CB in ASD infants, and on whether the rate of CB in infancy is diminished ([<reflink idref="bib28" id="ref21">28</reflink>]; [<reflink idref="bib53" id="ref22">53</reflink>]; [<reflink idref="bib73" id="ref23">73</reflink>]; [<reflink idref="bib75" id="ref24">75</reflink>]). Other research that has addressed autism likelihood in infants who have older autistic siblings has thus far primarily relied on automated analyses of all-day recordings that allow comparisons of vocal <emph>volubility</emph> (rate of overall infant vocalization) or vocal <emph>responsivity</emph> of parents and infants ([<reflink idref="bib66" id="ref25">66</reflink>]; [<reflink idref="bib71" id="ref26">71</reflink>]). These studies have not been able to identify canonical syllables because of limitations in the current capacity of automated detection.</p> <p>Recent work has produced the surprising finding of greater vocal volubility in male infants compared to females across the first year ([<reflink idref="bib48" id="ref27">48</reflink>]), but this research did not find evidence of sex differences specifically with regard to CB onset or rate. Higher volubility of males was confirmed for the first year in a study using automated analysis of recordings from nearly 6000 infants, but females in the study had higher volubility by the end of the second year ([<reflink idref="bib47" id="ref28">47</reflink>]). These findings suggest that we should be mindful of possible sex differences as we approach the comparison of autistic and nonautistic infants, since sex is clearly a factor that shows effects in autism. Specifically, autism occurs 3–4 times more in males than females ([<reflink idref="bib1" id="ref29">1</reflink>]; [<reflink idref="bib8" id="ref30">8</reflink>]; [<reflink idref="bib72" id="ref31">72</reflink>]), a pattern that has been attributed to a "female protective effect" ([<reflink idref="bib58" id="ref32">58</reflink>]; [<reflink idref="bib74" id="ref33">74</reflink>]) but may also reflect diagnostic biases with respect to characteristics attributed to the diagnostic criteria of ASD, which can potentially affect the rate at which females receive clinical services to support communication development ([<reflink idref="bib19" id="ref34">19</reflink>]; [<reflink idref="bib35" id="ref35">35</reflink>]).</p> <p>Socioeconomic status (SES) has been treated as an important factor in language acquisition for many decades ([<reflink idref="bib14" id="ref36">14</reflink>]; [<reflink idref="bib15" id="ref37">15</reflink>]; [<reflink idref="bib16" id="ref38">16</reflink>]; [<reflink idref="bib60" id="ref39">60</reflink>]; [<reflink idref="bib62" id="ref40">62</reflink>]; [<reflink idref="bib78" id="ref41">78</reflink>]), with common emphasis on either relatively low levels of infant-directed speech (IDS) among caregivers of lower SES ([<reflink idref="bib17" id="ref42">17</reflink>]) or low volubility of infants themselves in homes with lower SES ([<reflink idref="bib7" id="ref43">7</reflink>]). Considerable effort is being devoted to "closing the language gap" by training parents of lower SES to talk more and to talk more effectively with their infants ([<reflink idref="bib22" id="ref44">22</reflink>]; [<reflink idref="bib31" id="ref45">31</reflink>]). For the present work, a key issue may be the possible role of SES in CB, specifically because a recent article ([<reflink idref="bib69" id="ref46">69</reflink>]) reported late onset of CB in infants of lower SES, providing a contrasting empirical perspective on earlier reports of relative similarity between CB in infants of varying SES ([<reflink idref="bib7" id="ref47">7</reflink>]; [<reflink idref="bib45" id="ref48">45</reflink>]).</p> <p>The great majority of research on vocal and language development in infancy has been conducted in laboratories, where brief recordings are the common form of basic data ([<reflink idref="bib3" id="ref49">3</reflink>]; [<reflink idref="bib18" id="ref50">18</reflink>]; [<reflink idref="bib21" id="ref51">21</reflink>]; [<reflink idref="bib27" id="ref52">27</reflink>]). Recent developments have made it possible to conduct day-long recordings in infant homes ([<reflink idref="bib9" id="ref53">9</reflink>]; [<reflink idref="bib78" id="ref54">78</reflink>]). The result has been a vast body of new research that presumably yields more representative data about vocal development and the natural linguistic environment ([<reflink idref="bib11" id="ref55">11</reflink>]). On the contrary, day-long recordings have typically been analyzed only by automated procedures that yield less reliable data than human listening ([<reflink idref="bib5" id="ref56">5</reflink>]). In many instances, there are no well-established automated procedures to provide reliable data on key issues, such as the rate of CB. Our group has been among the most active in developing human coding methods to be used with randomly sampled segments from day-long recordings. By using real-time coding of many such segments with trained listeners, it is possible to obtain relatively large samples that can address issues such as rates of CB ([<reflink idref="bib34" id="ref57">34</reflink>]). Such research has broadened the perspective on infants as agents of their own vocal learning, highlighting the need to examine vocal production outside of contrived parent–infant interactions in the laboratory and suggesting CB as a particularly important measure in evaluating the underpinnings of language and potential differences in clinical populations.</p> <p>The present research represents the first extensive longitudinal effort to examine CB prospectively in TD and ASD infants across the entire first year of life in the natural home environment. This research is intended to (<reflink idref="bib1" id="ref58">1</reflink>) provide perspective on the robustness of vocal development in infants who commonly show important language delays, and (<reflink idref="bib2" id="ref59">2</reflink>) seek possible differences in the trajectories of CB development as part of a broader effort toward earlier detection of autism for the purposes of providing early intervention to engage individualized communication supports. To support these goals, our data will compare calculations of the <emph>canonical babbling ratio</emph> (CBR, the ratio of number of canonical syllables to all syllables in infant speech-like vocalizations) based on human coding of day-long recordings across the first year in TD and ASD infants. The CBR is the most commonly used metric of advanced prelinguistic vocal forms in infancy ([<reflink idref="bib29" id="ref60">29</reflink>]; [<reflink idref="bib30" id="ref61">30</reflink>]). We hypothesize that ASD infants will demonstrate lower CBR compared to TD infants beginning around 6 months of age. Our focus also includes consideration of the fact that autism occurs more commonly in males and that there may be sex differences in early vocal development, as suggested by our recent findings ([<reflink idref="bib48" id="ref62">48</reflink>]). Finally, we hypothesize that infants from families of lower SES will demonstrate lower CBR than infants from families of higher SES.</p> <hd id="AN0180988103-2">Method</hd> <p>The institutional review boards of Emory University (#IRB00059383 and #IRB00097674) and the University of Memphis (IRB #2143) approved the procedures used in this study. All families provided written consent prior to their participation in the longitudinal project from which the data in the present study were derived. No autistic people were directly involved in any of the areas mentioned; however, we have added a Community Involvement statement at the end of our manuscript indicating our community engagement work to support efforts promoting participation of autistic people in research and clinical services.</p> <hd id="AN0180988103-3">Participants</hd> <p>A total of 127 TD and 44 ASD infants (<emph>N</emph> = 171) were selected from a larger database of more than 300 infants who participated in a longitudinal sibling study of development across the first 3 years of life at the Marcus Autism Center in Atlanta, Georgia, USA. Families were recruited via flyers, advertisements, social media, and community referrals. Newborn infants were recruited in the larger sibling study as having either elevated likelihood for autism (at least one older biological sibling with a confirmed autism diagnosis) or low likelihood for autism[<reflink idref="bib8" id="ref63">8</reflink>] (no familial history of autism in first-, second-, or third-degree relatives). In the broader sample that we analyzed, 126 infants were determined at enrollment to have low likelihood of autism, of whom 100 were typically developing and 12 were diagnosed with autism, and 186 infants were determined to have elevated likelihood of autism, of whom 32 were diagnosed with autism and 27 had no clinical features. Caregivers were recruited as self-reported monolingual English speakers at birth; however, several caregivers were determined at a later point to be fluent in another language and non-English speakers were often present in many homes. Exclusionary criteria included birth complications (e.g. born preterm < 34 weeks, prenatal or perinatal trauma), evidence of a disorder influencing speech perception or production (e.g. hearing loss, cleft palate), unique genetic conditions associated with autism (e.g. Fragile X syndrome, tuberous sclerosis), and other medical conditions such as nonfebrile seizure disorders and requirement of tube feeding or ventilation.</p> <p>Recruitment was conducted without regard to sex or SES, but recordings were selected for coding to balance sex and SES measures to the extent possible in our sample given male-to-female ratios of autism and the demographics of the Atlanta, Georgia, USA metropolitan area. SES was measured as maternal education in years completed, beginning with Grade 1. The median SES for our entire sample was 18 (range = 6–25) years. The mean SES for ASD infants was 15.6 (<emph>SD</emph> = 3.06) years. For TD infants, the mean SES was 17.8 (<emph>SD</emph> = 2.58) years. Demographic information for our sample by outcome group is presented in Table 1.</p> <p>Table 1. Participant demographics and autism likelihood.</p> <p>Graph</p> <p> <ephtml> <table><colgroup><col align="left" /><col align="char" char="." /><col align="char" char="." /><col align="char" char="." /></colgroup><thead><tr><th align="left" colspan="2" rowspan="2">Group</th><th align="left" colspan="2">Outcome</th></tr><tr><th align="left">TD</th><th align="left">ASD</th></tr></thead><tbody><tr><td rowspan="2">Autism Likelihood</td><td>Low</td><td>100</td><td>12</td></tr><tr><td>Elevated</td><td>27</td><td>32</td></tr><tr><td rowspan="2">Sex</td><td>Male</td><td>71</td><td>29</td></tr><tr><td>Female</td><td>56</td><td>15</td></tr><tr><td rowspan="5"><bold>Race/Ethnicity</bold></td><td>White/Caucasian</td><td>104</td><td>27</td></tr><tr><td>Black/African American</td><td>14</td><td>11</td></tr><tr><td>Asian</td><td>1</td><td>2</td></tr><tr><td>Hawaiian or Pacific Islander</td><td>0</td><td>1</td></tr><tr><td>More than one Race</td><td>8</td><td>3</td></tr><tr><td rowspan="3"><bold>Socioeconomic status (SES)</bold></td><td>Mean (years of maternal education)</td><td>17.8</td><td>15.6</td></tr><tr><td>Standard Deviation</td><td>2.58</td><td>3.06</td></tr><tr><td>Range</td><td>12–30</td><td>6–25</td></tr></tbody></table> </ephtml> </p> <hd id="AN0180988103-4">Outcome classification</hd> <p>All infants received a full diagnostic characterization at both 2 and 3 years of age, including administration of the <emph>Autism Diagnostic Observation Schedule, 2nd Edition</emph> (ADOS-2; [<reflink idref="bib36" id="ref64">36</reflink>]). At each assessment, independent diagnostic impressions were assigned by two different senior-level clinicians—blind to risk status and prior diagnoses—based on clinical evaluation of available data. Assignment to TD and ASD outcome groups was determined by consensus, with clinician judgment taking priority over ADOS-2 diagnostic classifications.</p> <p>From our sample of 127 TD infants who demonstrated no clinical features at 2 or 3 years, 100 infants were originally designated at enrollment as having low likelihood and 27 were originally designated as having elevated likelihood for autism. In our sample of 44 infants later diagnosed with autism, 12 of the infants later diagnosed with autism were originally designated as having low likelihood for autism and 32 were originally designated as having elevated likelihood for autism.</p> <hd id="AN0180988103-5">Audio recording procedures</hd> <p>Families completed day-long recordings once a month from approximately 0 to 36 months. The present study used recording data collected between 0 and 13 months of age to observe the longitudinal trajectory of CB development across the critical period of its emergence. Audio recordings were completed using battery-powered LENA recording devices ([<reflink idref="bib10" id="ref65">10</reflink>]) secured inside the pocket of special clothing, capable of recording up to 16 hr of audio per charge. LENA devices have a 16 kHz sampling rate giving adequate audio play-back quality for human coding judgments of recorded material. Once a month, parents were provided with an LENA recording device and supplied regularly with appropriately sized clothing for their child to wear throughout the day, as well as full instructions on how to carry out recordings. The device was returned to the research project staff each month following recording days for data processing. Families of TD infants completed an average of 8.8 recordings (range = 4–13) across the ages studied and families of ASD infants completed an average of 8.1 recordings (range = 3–12), with an average recording time of approximately 11 hr per day.</p> <hd id="AN0180988103-6">Coder training</hd> <p>The coding procedures for the present study followed those conducted and described in prior studies from the University of Memphis Origin of Language Laboratories (OLL) using the longitudinal MAC/OLL data set ([<reflink idref="bib34" id="ref66">34</reflink>]; [<reflink idref="bib51" id="ref67">51</reflink>]). Coders and staff in Memphis, Tennessee, were blinded to all diagnostic and demographic information associated with each infant recording throughout the coding process. Our study involved 37 graduate student research assistants as coders in the OLL. All coders were female and enrolled in the graduate program for Communication Sciences and Disorders at the University of Memphis during the 7 years of coding.[<reflink idref="bib9" id="ref68">9</reflink>] Coders were trained in phonetic transcription as part of their graduate program and received intensive training for infant vocal coding by—depending on the cohort—the first, third, and/or the last authors on many coding parameters, including the differentiation of canonical and noncanonical syllables.</p> <p>During a 6- to 8-week coder training period, the coders met for weekly 1- to 2-hr lectures and presentation of audio examples of infant vocal types collated from laboratory recordings stored in the OLL archives. Each week, coders practiced labeling infant vocalizations as canonical or noncanonical while listening to 5-min recording segments. These practice segments were reviewed with the trainers during the lecture sessions each week. As needed, individual coders had sessions with the trainers to address coding discrepancies across trainees and based on coding by the last author, who is the longest-term researcher on vocal development among any of the OLL participants.</p> <p>Prior to the formal coding procedure, coders were required to have met standards of agreement across coders on training coding segments (to be within 10% of the counts on speech-like vocalizations as well as canonical and noncanonical syllables) usually by the sixth week of training. Additional training would otherwise ensue for individual coders until they could be fully certified. This training procedure is described in greater detail in prior published studies ([<reflink idref="bib34" id="ref69">34</reflink>]; [<reflink idref="bib48" id="ref70">48</reflink>], [<reflink idref="bib51" id="ref71">51</reflink>]).</p> <hd id="AN0180988103-7">Coding procedures</hd> <p>Prior to coding for canonical and noncanonical syllables, 21 five-minute segments were randomly extracted from each LENA recording. Each segment was coded in real time to obtain a count of infant utterances, which included speech precursors called "protophones" (both precanonical and canonical utterances) but not cries, laughs, or vegetative sounds ([<reflink idref="bib43" id="ref72">43</reflink>]). The utterance coding ([<reflink idref="bib37" id="ref73">37</reflink>]) is based on the "breath-group criterion"—vocalization marks the beginning and inhalation marks the end of an utterance. Using this procedure in the present study, we determined the number of infant protophones for a total of 1477 recordings (>31,000 five-minute segments).</p> <p>From the 21 segments of each recording, the eight segments with the highest number of infant utterances from this first pass of coding (see Supplementary Material for details of the selection process) were selected for a second pass of coding, where each of the eight segments was coded in real time by the same individual to obtain infant canonical and noncanonical syllable counts for each segment. More than 10,000 five-minute segments were coded in this second pass. Phase 2 segments had been selected for high volubility. Only 31 of the Phase 2 segments from either ASD or TD infants were later excluded on the basis of having no protophones at all, and consequently there were still >10,000 segments to be entered into the analysis of CBR. Approximately 330 min relevant to the CBR analysis were coded for each of the infants including all recordings from 0 through 13 months.</p> <hd id="AN0180988103-8">Coder agreement</hd> <p>A specific study was conducted to determine coder agreement on CBR and other coding features using LENA recordings and members of coding teams that participated in the data gathering for the present work. The study assigned nine "agreement coders" from among those who contributed to the data for the present work to recode 346 five-minute segments from 39 different infants that had been previously coded by another individual on one of the coding teams. In the assignments, we maximized the extent to which each agreement coder would recode segments from recordings from all age groups (0–2, 3–4, 5–6, 7–8, 9–10, and 11–13) and from all the previous coders. The agreement coders were assigned an average of ~38 segments (range = 18–72).[<reflink idref="bib10" id="ref74">10</reflink>]</p> <p>The results were segregated into two analyses, the first including segments from all ages of infants, resulting in a correlation between original and agreement coder values for CBR at <emph>r</emph> =.82. We then split the data to analyze CBR agreement for segments from recordings in only the 3 oldest age groups (7–8, 9–10, 11–13), because the youngest three age groups yielded CBR at near 0—as expected—a factor that artificially inflates correlations across the entire age range. For these three oldest age groups, the correlation for CBRs of 196 segments between the original and agreement coders was <emph>r</emph> =.78, which we take to represent a realistic estimate of the agreement among coders trained in accord with the OLL procedures. The mean CBR for the original coders across the 196 segments was.116 (<emph>SE</emph> =.01), and for the agreement coders was.121 (<emph>SE</emph> =.01).</p> <hd id="AN0180988103-9">Statistical analysis</hd> <p>Generalized estimating equations (GEEs) ([<reflink idref="bib33" id="ref75">33</reflink>]; [<reflink idref="bib77" id="ref76">77</reflink>]) were used as the basis for statistical analysis of our research questions. GEE-based approaches are an extension of the Generalized Linear Model (GLM), where dependent variables are assumed to be related to independent variables through a linear regression transformed by a link function, with the parameters of the regression estimated from sampled data by least-squares optimization ([<reflink idref="bib61" id="ref77">61</reflink>]). Unlike other approaches that model individual trajectories as functions of fixed and random effects, GEEs are marginal models that make inferences about population averages using a clustering variable to account for covariance between measures taken within a set of clusters, which in longitudinal designs will correspond to individual participants. Key advantages of GEE-based approaches are that they do not critically rely on distributional assumptions and continue to provide unbiased and consistent regression parameter estimates even when the covariance structure is mis-specified, provided that the sample size is adequate, the design is balanced and has comparable numbers of samples per group, and there are sufficient samples to allow the sample covariances to be reliably estimated.</p> <p>Since our study considers densely sampled longitudinal data within individuals, where we cannot easily identify distributional or correlational structure, and since we are interested in analyzing group differences rather than individual effects, we determined that GEEs were the most appropriate approach to adopt for statistical analysis.</p> <p>We used GEEs to investigate the effect of interactions between Age, Outcome, Sex, and SES on the emergence of CB over the first year of life. The CBR was chosen to be the single dependent variable, calculated for each daily recording as the ratio of the total number of canonical syllables summed across all segments coded within the recording to the total number of canonical and noncanonical syllables summed across all segments coded within the recording.</p> <p>The independent variables were Age, Outcome, Sex, and SES. Age was calculated in standardized months by multiplying the number of days since birth by 12/365. Data were grouped for plotting mean CBRs as follows: 0–2, 3–4, 5–6, 7–8, 9–10, and 11–13 months, with cutoffs at 2.5, 4.5, 6.5, 8.5, and 10.5 months, respectively. Biological sex of infants was determined to be male or female from parent report at enrollment. Outcome was ascertained from clinician best estimate based on clinical assessments conducted at 2 and 3 years. SES was analyzed as a continuous variable based on maternal education in years.</p> <p>For the purposes of the GEE analysis, data were assumed to be clustered within each participant, reflecting the longitudinal repeated-measures design of our study. The GEE model was specified assuming a Gaussian distribution for the dependent variable. GEE model parameters were estimated using maximum likelihood, and fit was considered by iteratively examining alternative covariance structures. Final models were based on an exchangeable correlation structure with a linear link function. Since our raw data showed clear evidence of nonlinearities, we also examined age factors combining intercept, linear, and quadratic terms; intercept and quadratic terms provided the best fit to the data and were retained.</p> <p>Tests for significant main effects and interactions in GEE are equivalent to testing whether the corresponding regression coefficients in the underlying Generalized Linear Model are significantly different from zero. This is most commonly determined using a Wald χ<sups>2</sups> statistic originally proposed by [<reflink idref="bib59" id="ref78">59</reflink>], from which the probability of rejecting the null hypothesis that each regression coefficient is zero can be calculated.</p> <p>Determination of meaningful differences between groups requires estimation of an effect size as well as the level of significance. There is no universally accepted definition of effect size for GEE analyses, and different authors have proposed using standardized regression coefficients, Cohen's <emph>f</emph><sups>2</sups>, and other alternatives, all of which are model-specific and difficult to compare with other analyses. To resolve this issue, [<reflink idref="bib67" id="ref79">67</reflink>] recently proposed a Robust Effect Size Index (RESI), based on M-estimators, which is widely applicable across many types of models, consistent under model misspecification, and can be written as a function of other established effect size estimators, permitting comparison across different models. By applying the definition of the RESI to the maximum-likelihood regression parameter estimates for the Generalized Linear Model implicit in the GEE approach, the effect size associated with any of the terms in the model can be shown to be a function of the Wald χ<sups>2</sups> statistics used to test for significance, defined by the noncentrality parameter of the Wald test statistic for the regression coefficients under the alternative hypothesis. By relating the scale of the RESI to scales of other established effect size estimators—notably Cohen's <emph>d</emph>—qualitative effect size ranges (small, small-to-medium, medium-to-large, large) can be used to interpret the RESI ([<reflink idref="bib67" id="ref80">67</reflink>]).</p> <p>To document our analyses, we provide GEE-derived regression coefficients and Wald test statistics for all main effects and interactions. Wald χ<sups>2</sups> statistics evaluate each associated null hypothesis with the corresponding <emph>p</emph> values, and RESI effect size estimates are derived from these statistics with bootstrapped 95% confidence intervals ([<reflink idref="bib24" id="ref81">24</reflink>]), together with RESI-derived Cohen's <emph>f</emph><sups>2</sups> effect sizes. A power analysis was not conducted because GEEs are only semi-parametric; they do not rely on specific distributions or assumptions about the data and are robust with balanced designs. All analyses were conducted in "R" ([<reflink idref="bib57" id="ref82">57</reflink>]) using the "geepack" and "ggeffects" packages ([<reflink idref="bib13" id="ref83">13</reflink>]) and the "RESI" package ([<reflink idref="bib23" id="ref84">23</reflink>]).</p> <hd id="AN0180988103-10">Results</hd> <p>Table 2 shows the main effects and interactions that were determined to be significant based on the Wald χ<sups>2</sups> values, together with the effect sizes and their confidence intervals. The Supplementary Material provides the full analysis including regression parameters and standard errors for the GEE analysis.</p> <p>Table 2. Results of GEE analysis for Age × Outcome × Sex × SES.</p> <p>Graph</p> <p> <ephtml> <table><colgroup><col align="left" /><col align="char" char="." /><col align="char" char="." /><col align="char" char="." /><col align="char" char="." /><col align="char" char="." /><col align="char" char="." /><col align="char" char="." /><col align="char" char="." /></colgroup><thead><tr><th align="left">Variable(s)</th><th align="left"><italic>df</italic></th><th align="left">Wald χ<sup>2</sup></th><th align="left"><italic>f</italic><sup>2</sup></th><th align="left">RESI</th><th align="left">2.5%</th><th align="left">97.5%</th><th align="left" colspan="2"><italic>p</italic> value</th></tr></thead><tbody><tr><td>Outcome</td><td>1</td><td>3.6</td><td>0.0154</td><td>0.124</td><td>0.00</td><td>0.398</td><td>0.057</td><td /></tr><tr><td>Sex</td><td>1</td><td>0.30</td><td>0.000</td><td>0.000</td><td>0.00</td><td>0.211</td><td>0.579</td><td /></tr><tr><td>SES</td><td>1</td><td>0.50</td><td>0.00436</td><td>0.000</td><td>0.00</td><td>0.195</td><td>0.493</td><td /></tr><tr><td>Age2</td><td>1</td><td>274</td><td>1.59</td><td>1.26</td><td>1.10</td><td>1.58</td><td>0.000</td><td><xref ref-type="table-fn" rid="tfn2">***</xref></td></tr><tr><td>Outcome:Sex</td><td>1</td><td>2.10</td><td>0.0656</td><td>0.0810</td><td>0.00</td><td>0.393</td><td>0.145</td><td /></tr><tr><td>Outcome:SES</td><td>1</td><td>0.00</td><td>0.00</td><td>0.000</td><td>0.00</td><td>0.239</td><td>0.920</td><td /></tr><tr><td>Sex:SES</td><td>1</td><td>0.00</td><td>0.00</td><td>0.000</td><td>0.00</td><td>0.215</td><td>0.833</td><td /></tr><tr><td>Outcome:Age2</td><td>1</td><td>1.20</td><td>0.0009</td><td>0.0300</td><td>0.00</td><td>0.322</td><td>0.283</td><td /></tr><tr><td>Sex:Age2</td><td>1</td><td>0.90</td><td>0.00</td><td>0.000</td><td>0.00</td><td>0.211</td><td>0.353</td><td /></tr><tr><td><bold>SES:Age</bold>2</td><td>1</td><td>0.50</td><td>0.00</td><td>0.000</td><td>0.00</td><td>0.233</td><td>0.500</td><td /></tr><tr><td>Outcome:Sex:SES</td><td>1</td><td>0.00</td><td>0.00</td><td>0.000</td><td>0.00</td><td>0.356</td><td>0.987</td><td /></tr><tr><td>Outcome:Sex:Age2</td><td>1</td><td>4.00</td><td>0.0172</td><td>0.131</td><td>0.00</td><td>0.378</td><td>0.047</td><td><xref ref-type="table-fn" rid="tfn2">*</xref></td></tr><tr><td>Outcome:SES:Age2</td><td>1</td><td>0.00</td><td>0.00</td><td>0.000</td><td>0.00</td><td>0.320</td><td>0.824</td><td /></tr><tr><td>Sex:SES:Age2</td><td>1</td><td>0.80</td><td>0.00</td><td>0.000</td><td>0.00</td><td>0.241</td><td>0.375</td><td /></tr><tr><td>Outcome:Sex:SES:Age2</td><td>1</td><td>0.70</td><td>0.00</td><td>0.000</td><td>0.00</td><td>0.411</td><td>0.387</td><td /></tr></tbody></table> </ephtml> </p> <p>1 Main effects and interactions, indicating significant effects based on the Wald χ<sups>2</sups> values, with RESI effect sizes and their 95% confidence intervals and RESI-derived <emph>f</emph><sups>2</sups> effect sizes.</p> <p>2 <emph>p</emph> < 0.05. **<emph>p</emph> < 0.01. ***<emph>p</emph> < 0.001.</p> <hd id="AN0180988103-11">Main effects: age, sex, SES, and outcome</hd> <p>A highly significant main effect of Age on CBR was found as expected (<emph>p</emph> < 0.001), reflecting increases in CB over the course of development. The effect size was large (RESI = 1.35: confidence interval (CI) = [1.35, 1.49]). No main effect for Outcome, Sex, or SES was found.</p> <p>The left and center panels of Figure 1 provide scatterplots showing the distribution of CBRs with age in normalized months for all the recordings. The right panel of Figure 1 shows the mean CBRs and bootstrapped standard error bars for the ASD and TD groups with ages binned in roughly 2-month intervals. While the TD group showed higher CBR at all ages after 6 months, the differences were small, and as indicated above, there was no main effect of Outcome. It is worth noting that in this GEE analysis, the main effect of Outcome approached significance (<emph>p</emph> = 0.057) with a small to medium effect size (RESI = 0.124: CI = [0.00, 0.398]), and therefore it is possible that a larger sample size might have produced the effect we predicted.</p> <p>Graph: Figure 1. Age × Outcome. (Left) Scatterplot of CBRs for all recordings corresponding to the age in months at each recording (ASD infants); (Center) Scatterplot of CBRs for all recordings corresponding to the age in months at each recording (TD infants); (Right) Mean CBRs with bootstrapped standard error bars for ASD and TD groups with ages binned in roughly 2-month intervals.</p> <hd id="AN0180988103-12">Interaction: age, sex, and outcome</hd> <p>The most important effect identified by the GEE analysis was a significant three-way interaction among Age, Sex, and Outcome (<emph>p</emph> = 0.047); male ASD infants showed significant differences in CB trajectories compared with female ASD infants, and to both male and female TD infants. The effect size for the interaction was medium (RESI = 0.131: CI = [0.00, 0.378]).</p> <p>The top row of panels in Figure 2 illustrates the pattern of the data, binned by age in the same way as in Figure 1, and again based on means and bootstrapped standard error bars across individual infants who contributed data at each of the ages. By 9–10 months, male ASD infants showed somewhat lower CB trajectories than their TD counterparts and female ASD infants showed somewhat higher CBR trajectories than TD controls. The bottom row of panels in Figure 2 shows the marginal regression lines and 95% confidence intervals determined from GEE modeling of the data. The GEE modeled data show divergence of the male TD and ASD groups by ~5 months, with minimal overlap of the confidence intervals beyond ~8–10 months. For the female infants, the divergence favoring the ASD infants was less strong, perhaps the result of higher variance among the smaller number of ASD females in the sample (15 females vs 29 males).</p> <p>Graph: Figure 2. Age × Outcome × Sex. (Top) Mean CBRs with bootstrapped standard error bars for Age × Outcome × Sex with ages binned in roughly 2-month intervals; (Bottom) Marginal regression lines and 95% confidence intervals showing dependence of canonical babbling ratio on age with interactions between Age, Outcome, and Sex.</p> <p>We observed no significant interaction among Age, SES, and Outcome (<emph>p</emph> = 0.824). We also observed no significant interaction among Age, Sex, and SES (<emph>p</emph> = 0.375). SES does not appear to influence the development of CB in our present sample.</p> <hd id="AN0180988103-13">Discussion</hd> <p>Our study provides the largest body of data to date evaluating vocal development prospectively across the whole first year of life in autistic infants. We compared CBRs from >590,000 syllables in 356 longitudinal day-long recordings of 44 ASD infants and 1121-day-long recordings of 127 TD infants. The recordings were human coded for both groups by highly trained individuals who were blind to age, autism likelihood, and diagnostic outcome of the infants.</p> <p>The study produced two important findings. First, the data indicate that the development of CB was delayed in the first year of life for male autistic infants. The smaller number of female autistic infants in the study (15 females vs 29 males) did not show the delay and even weakly showed higher CBRs than female TD infants. The findings thus provide further evidence for differences between children on the autism spectrum and those with typical development in the first year of life, although limited to males, on a vocal development factor related to the emergence of functional speech abilities ([<reflink idref="bib26" id="ref85">26</reflink>]; [<reflink idref="bib42" id="ref86">42</reflink>]; [<reflink idref="bib63" id="ref87">63</reflink>]). Without command of canonical syllables, it is widely accepted that infants are not ready to produce mature speech, which is overwhelmingly composed of canonical syllables ([<reflink idref="bib43" id="ref88">43</reflink>]).</p> <p>The sex differences observable in our data may support the notion of a "female protective effect" in autism ([<reflink idref="bib58" id="ref89">58</reflink>]), where developmental delays (that <emph>are</emph> found in autistic males) are thought to occur to a lesser extent in females. It is also possible that diagnostic bias could have distorted these data on sex. Prior work has demonstrated that autistic females are underdiagnosed and may demonstrate traits unique to the female autism phenotype not otherwise characterized in the diagnostic criteria for autism ([<reflink idref="bib19" id="ref90">19</reflink>]; [<reflink idref="bib35" id="ref91">35</reflink>]). Differential socialization of males and females may also play a role in the apparent "camouflaging" of female autism. Future studies using larger sample sizes of female autistic infants may further explore the extent to which high rates of CB at or above 9 months—a weak trend observed in our sample—may be a uniquely female biomarker for autism.</p> <p>The second important finding of the study concerns the robustness of the development of CB with regard to the factors we evaluated: Age, Outcome, Sex, and SES. Even in light of the significant interaction of Outcome, Sex, and Age, both groups of infants on average showed development of CB such that none of the individual factors other than Age had a significant main effect. Furthermore, the magnitude of the (nonsignificant) main effects was always relatively small when viewed with respect to mean values, and effect sizes were all small to medium: Males showed mean CBRs that were only ~11% lower than females, and ASD infants showed mean CBRs that were only ~23% lower than TD infants, with no significant effect of SES, all during the time period when the CB stage is expected to be in place (i.e. beyond ~6 months). These data patterns reflect considerable overlap between the CBR values for all these groups. We do not present this robustness argument to detract from proven differences in CB between the groups or from possible differences that may be found in the future. On the contrary, we emphasize that the small differences that have been found should be pursued as possible markers of need for specialized clinical services to support communication outcomes, for example, speech and language therapy, based on individual developmental profiles. We also, however, emphasize that so far these differences have been relatively small in effect size.</p> <p>We interpret the overall similarity of CBRs across all the infant groups as providing further evidence that CB is a feature of human capability that is deeply canalized, presumably because without the ability to produce canonical syllables, an infant is not ready to produce speech ([<reflink idref="bib43" id="ref92">43</reflink>]). This interpretation is based on the fact that the vast majority of utterances in natural languages are composed overwhelmingly of canonical syllables. It seems nature has provided a firm foundation for the development of CB, so that even conditions characterized by social communication impairment do not demonstrate large differences in their production of mature syllables prior to the emergence of speech. Even the male ASD group had mean CBRs that differed across the age range beyond 6 months by less than half a standard deviation from the mean CBRs of TD infants, despite the wide variation in individual CBR trajectories found in both autistic and TD groups. Future work will also seek to examine CB differences with regard to their relation to specific autism characteristics such as nonverbal and low verbal forms of autism, as well as co-occurring intellectual disabilities, to help make possible individualized early communication supports for autistic children. Such research may be able to detect important differences in CB between TD infants and infants with ASD that have thus far eluded us.</p> <p>Prior autism research on possible differences in CB has revealed mixed evidence. The majority of prior studies have reported infants and children with an elevated likelihood or later-confirmed diagnosis demonstrate lower rates of CB compared to TD infants ([<reflink idref="bib20" id="ref93">20</reflink>]; [<reflink idref="bib50" id="ref94">50</reflink>]; [<reflink idref="bib53" id="ref95">53</reflink>]; [<reflink idref="bib54" id="ref96">54</reflink>]; [<reflink idref="bib55" id="ref97">55</reflink>]; [<reflink idref="bib56" id="ref98">56</reflink>]; [<reflink idref="bib73" id="ref99">73</reflink>]; [<reflink idref="bib75" id="ref100">75</reflink>]), but they have tended to employ different methodologies to study vocal development ([<reflink idref="bib28" id="ref101">28</reflink>]; [<reflink idref="bib76" id="ref102">76</reflink>]). For example, while our study and that of [<reflink idref="bib75" id="ref103">75</reflink>] compared infant groups on CBR as a parameter, other studies have focused on the onset of the CB stage as reflected in CBR measured from home movies ([<reflink idref="bib53" id="ref104">53</reflink>]) or on the onset of reduplicated babbling as reported by parents ([<reflink idref="bib20" id="ref105">20</reflink>]). Two other efforts have addressed the rate of CB in children with and without autism through two different methods of automated analysis ([<reflink idref="bib50" id="ref106">50</reflink>]; [<reflink idref="bib56" id="ref107">56</reflink>]). The various studies have also differed enormously in the range of ages evaluated and the nature of the recordings that were used to acquire CB data.</p> <p>The study with the greatest similarity to the present one is [<reflink idref="bib75" id="ref108">75</reflink>] (hereafter Y2022), who also studied CBR in autistic and TD infants. But even in the case of Y2022, the methodological differences with our study were substantial. While our data were collected in infant homes using day-long recordings, with 8 five-minute segments selected for real-time human coding from each recording, Y2022 used repeat-observation coding of recordings of 10–30 min that were obtained during administration of autism or communication assessments. Our study was larger in scope, with 8- to 9-day-long recordings per infant and a total of >4000 syllables coded per infant across the ages from 0 to 13 months. At the two ages of recordings in Y2022, their Table 2 suggests an average of ~53 syllables per infant were coded at 6 months and ~119 at 12 months, while our study produced >800 syllables per infant during the period from 5 to 6 months and >900 during the period from 11 to 13 months. The calculation of the CBR was also notably different because Y2022 excluded "non-speech-like" utterances, which appears to have involved the omission of a great many utterances (such as squeals, growls, and vocants without consonant-like supra-glottal articulations) in their calculations of CBR. In contrast, these types of utterances <emph>were</emph> included in the denominators of the calculations for the present paper. The lack of inclusion of the utterances deemed by Y2022 to be non-speech-like may account for the fact that the rate of vocalizations they found (2–3 per minute) was substantially lower than has been found in laboratory recordings in the OLL, where the rate tends to be 6–8 per minute—even in day-long home recordings, the OLL has reported rates of 4–5 protophones per minute for infants who are awake ([<reflink idref="bib51" id="ref109">51</reflink>]). Perhaps most important, the participant groups also differed substantially in that the ASD group for Y2022 included a >6:1 ratio of males to females, while in the present study, that ratio was <2:1.</p> <p>Taking into account all these differences of methods, we note that Y2022 reported significantly lower CBRs in autistic infants than in TD infants, while we found no such main effect of Outcome, although we note that the analysis in our study indicated a <emph>p</emph> value of 0.057 for that potential main effect. The most important effect we have reported here is the significant three-way interaction between Age, Sex, and Outcome, where Sex appeared to be a critical factor—only the autistic males showed low CBRs at the age ranges where CB routinely occurs, while the autistic females showed no such differences. Y2022 noted that Sex was a significant covariate in their analysis, with females showing higher CBR (although there were only six ASD females).</p> <p>We are left with a difficult interpretation, among other things, because it is not clear why the sex ratio of autistic participants was so different across the studies. And given that the sex ratio difference was large, it is not clear whether the main effect found in Y2022 may have occurred instead of an interaction with Sex because of the small number of autistic females in the sample or whether the lack of a main effect of ASD in our own study may have occurred because the large number of autistic females in the sample may have inhibited it. Hopefully additional research will be able to shed further light on these discrepancies between the studies.</p> <p>Y2022 reported an intriguing interaction: Infants with elevated likelihood for autism were separated into four subgroups in their study: those who (<reflink idref="bib1" id="ref110">1</reflink>) received the diagnosis and <emph>did</emph> show a language delay, (<reflink idref="bib2" id="ref111">2</reflink>) received the diagnosis and <emph>did not</emph> show a language delay, (<reflink idref="bib3" id="ref112">3</reflink>) did not receive the diagnosis and <emph>did</emph> show a language delay, and (<reflink idref="bib4" id="ref113">4</reflink>) did not receive the diagnosis and <emph>did not</emph> show a language delay. Of these four groups, only the fourth showed CBRs comparable to their low likelihood group. Our study did not attempt comparisons of all these possibilities, because the broader sample from which the 171 infants were drawn is still under evaluation. We only focused here on infants with a confirmed later diagnosis of autism and infants who showed no sign of any clinical condition at the points of evaluation that have been completed. Our report did not include measures of language performance; however, future studies using this data set are planned to examine CB development in the context of later language abilities, using the same groups of infants and additional ones whose diagnostic data are still being collected. We hope then to be able to offer further evidence using day-long recordings on the intriguing interaction found in Y2022.</p> <p>Our study indicates discernibly low mean CB trajectories for male autistic infants beginning around 9 months of age, but we note that the individual trajectories in all groups spanned a broad range, reflecting a spectrum of ability and impairment. For those infants who do show delays in CB by 12 months, referrals to speech and language services may be warranted to engage communication supports to maximize outcomes for these children and their families. Although SES did not show a significant main effect, trends in the data also suggest low SES may be associated with low CBR, especially in males who show signs of autism. Despite there being mixed prior evidence on the effect of SES on CB development, these trends echo prior studies pointing to environmental influences on early language development that has the additional potential to be affected by sex differences ([<reflink idref="bib7" id="ref114">7</reflink>]; [<reflink idref="bib69" id="ref115">69</reflink>]).</p> <p>As we have indicated, none of the factors we studied other than Age appeared to have a significant main effect on CB. Thus far, only deafness and Williams syndrome have been shown to have dramatic effects that, for example, delay the onset of CB by many months ([<reflink idref="bib6" id="ref116">6</reflink>]; [<reflink idref="bib68" id="ref117">68</reflink>]; [<reflink idref="bib70" id="ref118">70</reflink>]). The present results and even those of Y2022 show more moderate effects of factors such as autism outcome, sex, and SES, highlighting the robust nature of vocal emergence for speech development across human infants.</p> <p>Ours is the largest study to date of CB development in the first year of life using home-based day-long recordings and human coding. It should be noted that the CBR criterion commonly used to represent attainment of the CB stage (≥ 0.15) (see [<reflink idref="bib43" id="ref119">43</reflink>] and [<reflink idref="bib41" id="ref120">41</reflink>] for commentary) was only reached on average by 11–13 months of age by our participants, and this pattern applied to both the TD and ASD groups. Prior studies using laboratory-based recordings have found that TD infants generally reach this criterion by 7–10 months of age. This discrepancy highlights clear differences in CBRs obtained from laboratory versus day-long recordings ([<reflink idref="bib32" id="ref121">32</reflink>]; [<reflink idref="bib34" id="ref122">34</reflink>]), and also emphasizes the ongoing need to establish an appropriate CBR criterion for home-based recorded observations as opposed to laboratory recorded observations or parent-reported CB onset.</p> <hd id="AN0180988103-14">Limitations</hd> <p>To the best of our ability, our sample of infants was recruited equitably and reflects the reported sex ratios for autism, the demographics of the recruitment region, and the constraints imposed by participation in an intensive longitudinal study; however, the effort resulted in an unequal sample size of participants across groups, including a small number of autistic females (<emph>n</emph> = 15) and fewer autistic infants from higher SES families, despite being the largest day-long recording sample to date. We note that the GEEs used for statistical analysis are robust against small sample sizes and provide conservative assessments of longitudinal effects. It should be noted that our recruitment efforts for sibling-based autism likelihood excluded genetic or syndromic forms of autism (i.e., Rett and Fragile X syndromes). Future studies may seek to examine the relationship between CB and specific traits of children across the autism spectrum to help determine appropriate early detection and communication supports. Finally, with respect to potential confounds of sibling studies, parents of infants with elevated likelihood for autism may use targeted language development strategies given their likely prior experiences or training provided in early intervention with their infants' older siblings. Future studies may seek to examine the presence and effect of parent interaction differences across autistic infants whose parents had or had not previously participated in early intervention support services for language development.</p> <p>The present study did not include analyses of outcome measures for language. As stated, future studies using these and other data from the larger longitudinal study are planned to examine the relationship between infant CB and later autism traits, including social characteristics, linguistic abilities, and restricted/repetitive behaviors, from data collected as part of the larger longitudinal project. Also, our study focused entirely on the emergence of CB, yet recent studies have also shown volubility differences across age for males and females, and we view it as important to assess these issues in autism likelihood groups ([<reflink idref="bib48" id="ref123">48</reflink>]). Future studies are also planned to examine volubility differences in our data set of day-long recordings in the context of known diagnostic outcomes for autism, given recent reports of "hypervocality" in infants with an elevated likelihood for autism ([<reflink idref="bib66" id="ref124">66</reflink>]).</p> <hd id="AN0180988103-15">Conclusion</hd> <p>Our findings indicate that the development of CB is delayed in the first year of life in autistic infants, but that this is a small effect that is limited to male infants. The results hint at unique sex differences in the vocal development of autistic infants in the second half-year of life. The study provides further evidence of the robustness of CB, the development of which has shown relatively small effects across many clinical diagnoses, high and low SES, and male and female infants. Our results support clinical discussions with families to engage individualized communication supports in early intervention for infants with unexpected CB trajectories in order to maximize communication outcomes in autistic children.</p> <hd id="AN0180988103-16">Supplemental Material</hd> <p>Graph: Supplemental material, sj-docx-1-aut-10.1177_13623613241253908 for Canonical babbling trajectories across the first year of life in autism and typical development by Helen L. Long, Gordon Ramsay, Edina R. Bene, Pumpki Lei Su, Hyunjoo Yoo, Cheryl Klaiman, Stormi L Pulver, Shana Richardson, Moira L. Pileggi, Natalie Brane and D. Kimbrough Oller in Autism</p> <p>The authors wish to thank the participating families in the Atlanta, GA, area for their time and dedication to the longitudinal component of this project. 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Pediatrics, 124(1), 342–349.</bibtext> </blist> </ref> <ref id="AN0180988103-18"> <title> Footnotes </title> <blist> <bibtext> The authors confirm contribution to the paper as follows: study conception and design: H.L.L., G.R., E.R.B., and D.K.O.; data collection and clinical assessment: G.R., C.K., S.L.P., S.R., M.L.P., and N.B.; data coding, analysis, and interpretation of results: H.L.L., G.R., E.R.B., P.L.S., H.Y., and D.K.O.; draft manuscript preparation: H.L.L., G.R., D.K.O., P.L.S., E.R.B., and H.Y. All authors reviewed the results and approved the final version of the manuscript.</bibtext> </blist> <blist> <bibtext> Raw audio recordings are identifiable and restrictions on access are necessary to protect the privacy and confidentiality of participants due to HIPAA requirements. Deidentified data analyzed from those recordings in our manuscript are available on the Open Science Framework at https://osf.io/zea63/.</bibtext> </blist> <blist> <bibtext> The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: D.K.O. is an unpaid member of the LENA Scientific Advisory Board. No other authors have any competing interests to report.</bibtext> </blist> <blist> <bibtext> The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Research reported in this publication was supported in part by NICHD Grants T32HD007489 and U54HD090256 (Trainee: H.L.L.), NCATS Grants TL1TR002375 and UL1TR002373 (Trainee: H.L.L.), NIDCD Grant R01DC015108 (PI: D.K.O., Subaward PI: G.R.), and NIMH Grant P50MH100029 (Co-PI: G.R.). Additional support was provided by the Plough Foundation, the Holly Lane Foundation, the Marcus Foundation, the Woodruff-Whitehead Foundation, and the Georgia Research Alliance.</bibtext> </blist> <blist> <bibtext> G.R. directs a High-School Research Internship in ASD where high-school autistic students are welcomed into the Spoken Communication Laboratory at the Marcus Autism Center and actively involved in research projects in any way that is meaningful to them. Autistic teenagers employed through this program have been involved in the analysis of data on research projects arising from the Emory Autism Center for Excellence (ACE) (NIH P50 MH100029). G.R. also directs the Marcus Fellowship in Speech Science and Engineering, a pre-doctoral fellowship program open to anyone with an undergraduate degree interested in pursuing autism research. Two siblings of autistic children were employed through this fellowship and provided feedback and perspective on our entire research program; they also conducted their own research projects using data from the Emory ACE. One of the lab managers employed by the Spoken Communication Laboratory was an autistic woman and helped with data collection for the Emory ACE. None of these individuals was directly involved with the preparation of the present paper, but we are providing this information as evidence of our programmatic commitment to engaging the autistic community in research.</bibtext> </blist> <blist> <bibtext> Helen L. Long</bibtext> </blist> <blist> <bibtext>Graph</bibtext> </blist> <blist> <bibtext>https://orcid.org/0000-0001-6406-1222 Pumpki Lei Su</bibtext> </blist> <blist> <bibtext>Graph https://orcid.org/0000-0002-9392-360X</bibtext> </blist> <blist> <bibtext> Supplemental material for this article is available online.</bibtext> </blist> <blist> <bibtext> Of the 100 children originally classified as having a low likelihood for autism, 93 had at least one older nonautistic sibling and seven were first-borns.</bibtext> </blist> <blist> <bibtext> Hearing impairment was present in at least two coders, but there was no evidence that they were less reliable than other coders.</bibtext> </blist> <blist> <bibtext> The variation was based in the availability of coders given their class and clinic schedules and the amount of time they could reasonably allocate to the agreement effort.</bibtext> </blist> </ref> <aug> <p>By Helen L. Long; Gordon Ramsay; Edina R. Bene; Pumpki Lei Su; Hyunjoo Yoo; Cheryl Klaiman; Stormi L Pulver; Shana Richardson; Moira L. Pileggi; Natalie Brane and D. Kimbrough Oller</p> <p>Reported by Author; Author; Author; Author; Author; Author; Author; Author; Author; Author; Author</p> </aug> <nolink nlid="nl1" bibid="bib25" firstref="ref1"></nolink> <nolink nlid="nl2" bibid="bib63" firstref="ref2"></nolink> <nolink nlid="nl3" bibid="bib26" firstref="ref3"></nolink> <nolink nlid="nl4" bibid="bib42" firstref="ref4"></nolink> <nolink nlid="nl5" bibid="bib49" firstref="ref5"></nolink> <nolink nlid="nl6" bibid="bib52" firstref="ref6"></nolink> <nolink nlid="nl7" bibid="bib28" firstref="ref7"></nolink> <nolink nlid="nl8" bibid="bib40" firstref="ref8"></nolink> <nolink nlid="nl9" bibid="bib46" firstref="ref9"></nolink> <nolink nlid="nl10" bibid="bib64" firstref="ref10"></nolink> <nolink nlid="nl11" bibid="bib65" firstref="ref11"></nolink> <nolink nlid="nl12" bibid="bib44" firstref="ref12"></nolink> <nolink nlid="nl13" bibid="bib68" firstref="ref14"></nolink> <nolink nlid="nl14" bibid="bib70" firstref="ref15"></nolink> <nolink nlid="nl15" bibid="bib39" firstref="ref16"></nolink> <nolink nlid="nl16" bibid="bib37" firstref="ref17"></nolink> <nolink nlid="nl17" bibid="bib12" firstref="ref20"></nolink> <nolink nlid="nl18" bibid="bib53" firstref="ref22"></nolink> <nolink nlid="nl19" bibid="bib73" firstref="ref23"></nolink> <nolink nlid="nl20" bibid="bib75" firstref="ref24"></nolink> <nolink nlid="nl21" bibid="bib66" firstref="ref25"></nolink> <nolink nlid="nl22" bibid="bib71" firstref="ref26"></nolink> <nolink nlid="nl23" bibid="bib48" firstref="ref27"></nolink> <nolink nlid="nl24" bibid="bib47" firstref="ref28"></nolink> <nolink nlid="nl25" bibid="bib72" firstref="ref31"></nolink> <nolink nlid="nl26" bibid="bib58" firstref="ref32"></nolink> <nolink nlid="nl27" bibid="bib74" firstref="ref33"></nolink> <nolink nlid="nl28" bibid="bib19" firstref="ref34"></nolink> <nolink nlid="nl29" bibid="bib35" firstref="ref35"></nolink> <nolink nlid="nl30" bibid="bib14" firstref="ref36"></nolink> <nolink nlid="nl31" bibid="bib15" firstref="ref37"></nolink> <nolink nlid="nl32" bibid="bib16" firstref="ref38"></nolink> <nolink nlid="nl33" bibid="bib60" firstref="ref39"></nolink> <nolink nlid="nl34" bibid="bib62" firstref="ref40"></nolink> <nolink nlid="nl35" bibid="bib78" firstref="ref41"></nolink> <nolink nlid="nl36" bibid="bib17" firstref="ref42"></nolink> <nolink nlid="nl37" bibid="bib22" firstref="ref44"></nolink> <nolink nlid="nl38" bibid="bib31" firstref="ref45"></nolink> <nolink nlid="nl39" bibid="bib69" firstref="ref46"></nolink> <nolink nlid="nl40" bibid="bib45" firstref="ref48"></nolink> <nolink nlid="nl41" bibid="bib18" firstref="ref50"></nolink> <nolink nlid="nl42" bibid="bib21" firstref="ref51"></nolink> <nolink nlid="nl43" bibid="bib27" firstref="ref52"></nolink> <nolink nlid="nl44" bibid="bib11" firstref="ref55"></nolink> <nolink nlid="nl45" bibid="bib34" firstref="ref57"></nolink> <nolink nlid="nl46" bibid="bib29" firstref="ref60"></nolink> <nolink nlid="nl47" bibid="bib30" firstref="ref61"></nolink> <nolink nlid="nl48" bibid="bib36" firstref="ref64"></nolink> <nolink nlid="nl49" bibid="bib10" firstref="ref65"></nolink> <nolink nlid="nl50" bibid="bib51" firstref="ref67"></nolink> <nolink nlid="nl51" bibid="bib43" firstref="ref72"></nolink> <nolink nlid="nl52" bibid="bib33" firstref="ref75"></nolink> <nolink nlid="nl53" bibid="bib77" firstref="ref76"></nolink> <nolink nlid="nl54" bibid="bib61" firstref="ref77"></nolink> <nolink nlid="nl55" bibid="bib59" firstref="ref78"></nolink> <nolink nlid="nl56" bibid="bib67" firstref="ref79"></nolink> <nolink nlid="nl57" bibid="bib24" firstref="ref81"></nolink> <nolink nlid="nl58" bibid="bib57" firstref="ref82"></nolink> <nolink nlid="nl59" bibid="bib13" firstref="ref83"></nolink> <nolink nlid="nl60" bibid="bib23" firstref="ref84"></nolink> <nolink nlid="nl61" bibid="bib20" firstref="ref93"></nolink> <nolink nlid="nl62" bibid="bib50" firstref="ref94"></nolink> <nolink nlid="nl63" bibid="bib54" firstref="ref96"></nolink> <nolink nlid="nl64" bibid="bib55" firstref="ref97"></nolink> <nolink nlid="nl65" bibid="bib56" firstref="ref98"></nolink> <nolink nlid="nl66" bibid="bib76" firstref="ref102"></nolink> <nolink nlid="nl67" bibid="bib41" firstref="ref120"></nolink> <nolink nlid="nl68" bibid="bib32" firstref="ref121"></nolink>
Header DbId: eric
DbLabel: ERIC
An: EJ1450083
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PubType: Academic Journal
PubTypeId: academicJournal
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Items – Name: Title
  Label: Title
  Group: Ti
  Data: Canonical Babbling Trajectories across the First Year of Life in Autism and Typical Development
– Name: Language
  Label: Language
  Group: Lang
  Data: English
– Name: Author
  Label: Authors
  Group: Au
  Data: <searchLink fieldCode="AR" term="%22Helen+L%2E+Long%22">Helen L. Long</searchLink> (ORCID <externalLink term="https://orcid.org/0000-0001-6406-1222">0000-0001-6406-1222</externalLink>)<br /><searchLink fieldCode="AR" term="%22Gordon+Ramsay%22">Gordon Ramsay</searchLink><br /><searchLink fieldCode="AR" term="%22Edina+R%2E+Bene%22">Edina R. Bene</searchLink><br /><searchLink fieldCode="AR" term="%22Pumpki+Lei+Su%22">Pumpki Lei Su</searchLink> (ORCID <externalLink term="https://orcid.org/0000-0002-9392-360X">0000-0002-9392-360X</externalLink>)<br /><searchLink fieldCode="AR" term="%22Hyunjoo+Yoo%22">Hyunjoo Yoo</searchLink><br /><searchLink fieldCode="AR" term="%22Cheryl+Klaiman%22">Cheryl Klaiman</searchLink><br /><searchLink fieldCode="AR" term="%22Stormi+L%2E+Pulver%22">Stormi L. Pulver</searchLink><br /><searchLink fieldCode="AR" term="%22Shana+Richardson%22">Shana Richardson</searchLink><br /><searchLink fieldCode="AR" term="%22Moira+L%2E+Pileggi%22">Moira L. Pileggi</searchLink><br /><searchLink fieldCode="AR" term="%22Natalie+Brane%22">Natalie Brane</searchLink><br /><searchLink fieldCode="AR" term="%22D%2E+Kimbrough+Oller%22">D. Kimbrough Oller</searchLink>
– Name: TitleSource
  Label: Source
  Group: Src
  Data: <searchLink fieldCode="SO" term="%22Autism%3A+The+International+Journal+of+Research+and+Practice%22"><i>Autism: The International Journal of Research and Practice</i></searchLink>. 2024 28(12):3078-3091.
– Name: Avail
  Label: Availability
  Group: Avail
  Data: SAGE Publications. 2455 Teller Road, Thousand Oaks, CA 91320. Tel: 800-818-7243; Tel: 805-499-9774; Fax: 800-583-2665; e-mail: journals@sagepub.com; Web site: https://sagepub.com
– Name: PeerReviewed
  Label: Peer Reviewed
  Group: SrcInfo
  Data: Y
– Name: Pages
  Label: Page Count
  Group: Src
  Data: 14
– Name: DatePubCY
  Label: Publication Date
  Group: Date
  Data: 2024
– Name: SourceSuprt
  Label: Sponsoring Agency
  Group: SrcSuprt
  Data: Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) (DHHS/NIH)<br />National Center for Advancing Translational Sciences (NCATS) (DHHS/NIH)<br />National Institute on Deafness and Other Communication Disorders (NIDCD) (DHHS/NIH)<br />National Institute of Mental Health (NIMH) (DHHS/NIH)
– Name: NumberContract
  Label: Contract Number
  Group: NumCntrct
  Data: T32HD007489<br />U54HD090256<br />TL1TR002375<br />UL1TR002373<br />R01DC015108<br />P50MH100029
– Name: TypeDocument
  Label: Document Type
  Group: TypDoc
  Data: Journal Articles<br />Reports - Research
– Name: Subject
  Label: Descriptors
  Group: Su
  Data: <searchLink fieldCode="DE" term="%22Infants%22">Infants</searchLink><br /><searchLink fieldCode="DE" term="%22Infant+Behavior%22">Infant Behavior</searchLink><br /><searchLink fieldCode="DE" term="%22Child+Language%22">Child Language</searchLink><br /><searchLink fieldCode="DE" term="%22Oral+Language%22">Oral Language</searchLink><br /><searchLink fieldCode="DE" term="%22Autism+Spectrum+Disorders%22">Autism Spectrum Disorders</searchLink><br /><searchLink fieldCode="DE" term="%22Child+Development%22">Child Development</searchLink><br /><searchLink fieldCode="DE" term="%22Symptoms+%28Individual+Disorders%29%22">Symptoms (Individual Disorders)</searchLink><br /><searchLink fieldCode="DE" term="%22Syllables%22">Syllables</searchLink><br /><searchLink fieldCode="DE" term="%22Gender+Differences%22">Gender Differences</searchLink><br /><searchLink fieldCode="DE" term="%22Coding%22">Coding</searchLink><br /><searchLink fieldCode="DE" term="%22Interrater+Reliability%22">Interrater Reliability</searchLink><br /><searchLink fieldCode="DE" term="%22Socioeconomic+Status%22">Socioeconomic Status</searchLink>
– Name: DOI
  Label: DOI
  Group: ID
  Data: 10.1177/13623613241253908
– Name: ISSN
  Label: ISSN
  Group: ISSN
  Data: 1362-3613<br />1461-7005
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: This study explores vocal development as an early marker of autism, focusing on canonical babbling rate and onset, typically established by 7 months. Previous reports suggested delayed or reduced canonical babbling in infants later diagnosed with autism, but the story may be complicated. We present a prospective study on 44 infants later diagnosed with autism spectrum disorder compared with 127 infants later identified as typically developing who were followed longitudinally with day-long recordings from 0 to 13 months. Eight 5-min segments from each of their recordings were coded for canonical and noncanonical syllables. The results confirmed many reports that canonical babbling is a robust feature of human vocal development in the first year of life, with small overall mean differences in canonical babbling rates between the autism spectrum disorder and typically developing groups beginning around 9 months, primarily in males. Our findings highlight the importance of considering sex differences in vocal communication as part of the early detection and diagnosis of autism when determining the need for communication supports to maximize outcomes.
– Name: AbstractInfo
  Label: Abstractor
  Group: Ab
  Data: As Provided
– Name: Note
  Label: Notes
  Group: Note
  Data: https://osf.io/zea63
– Name: DateEntry
  Label: Entry Date
  Group: Date
  Data: 2024
– Name: AN
  Label: Accession Number
  Group: ID
  Data: EJ1450083
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=eric&AN=EJ1450083
RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1177/13623613241253908
    Languages:
      – Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 14
        StartPage: 3078
    Subjects:
      – SubjectFull: Infants
        Type: general
      – SubjectFull: Infant Behavior
        Type: general
      – SubjectFull: Child Language
        Type: general
      – SubjectFull: Oral Language
        Type: general
      – SubjectFull: Autism Spectrum Disorders
        Type: general
      – SubjectFull: Child Development
        Type: general
      – SubjectFull: Symptoms (Individual Disorders)
        Type: general
      – SubjectFull: Syllables
        Type: general
      – SubjectFull: Gender Differences
        Type: general
      – SubjectFull: Coding
        Type: general
      – SubjectFull: Interrater Reliability
        Type: general
      – SubjectFull: Socioeconomic Status
        Type: general
    Titles:
      – TitleFull: Canonical Babbling Trajectories across the First Year of Life in Autism and Typical Development
        Type: main
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            NameFull: Helen L. Long
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            NameFull: Natalie Brane
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          Dates:
            – D: 01
              M: 12
              Type: published
              Y: 2024
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              Value: 28
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              Value: 12
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            – TitleFull: Autism: The International Journal of Research and Practice
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