Investigating the Relationship Between Early Speech Milestones and Oral–Motor Development in Infants

ABSTRACT

Aim

This study aimed to determine whether infants' oromotor skills were related to the onset of babbling and their phonetic inventory at 6 months of age.

Methods

Parents of 50 6‐month‐old infants (41 full‐term, 9 preterm) completed the Child Oral and Motor Proficiency Scale (ChOMPS), a valid and reliable caregiver‐report measure of oromotor, feeding, and gross motor development. Caregivers additionally reported information about their infant's babbling and perceived phonetic inventory, or protophones, via an online questionnaire.

Results

Linear regression analysis revealed a statistically significant positive association between ChOMPS scores at 6 months and the number of different protophones parents reported that the infant produced. Logistic regression modelling showed that infants' ChOMPS scores significantly predicted their likelihood of babbling by 6 months of age. Preterm status and sex were not associated with babbling onset or phonetic inventory.

Conclusion

These findings suggest a possible link between early oromotor development and emerging speech abilities in infancy. Infants with stronger oromotor skills at 6 months tended to produce a larger variety of protophones and were more likely to be early babblers, per parent report. These results reveal the potential value of early oromotor behaviours as indicators of developing speech skills.

Summary

• We examined the relationship between infants' oromotor skills, the onset of babbling, and the number of consonant and vowel‐like protophones produced at 6 months of age.

• Oromotor skills were positively associated with the number of different consonant and vowel‐like protophones parents perceived their infants produced at 6 months, and infants who had started babbling at 6 months demonstrated higher oromotor scores.

• These findings suggest a potential link between early oromotor development and emerging speech abilities in infancy.

Abbreviation

ChOMPS

Child Oral and Motor Proficiency Scale

1. Introduction

Infancy is a period of rapid motor and communication development. In terms of feeding, infants progress from drinking only human milk and/or formula to eating solid foods. Communication develops from early vocalisations to the emergence of first words. Though often studied separately, oromotor (e.g., the movements of the jaw, tongue, mouth, and lips) and speech language development are interacting, closely related systems [1]. Oral feeding and speech production rely on common musculature [2], and both require oromotor coordination, planning, and execution supported by shared neural processes [3]. Early feeding difficulty is associated with heightened risk for delayed speech and language abilities [4], further emphasising their connections. Despite their interconnectedness, speech production and feeding have distinct coordinative patterns, developmental trajectories, and end goals [5], making their association an ongoing subject of research interest.

The frame/content theory proposes that early speech production emerges directly from patterns of jaw movement needed for feeding [6]. Specifically, infants first demonstrate reciprocal open‐closed jaw movements during chewing and sucking, which provide the motor “frame” needed for subsequent production of babbling. Conversely, some studies examining the relationship between speech development and development of other oromotor functions have suggested that speech coordination emerges separately from other oromotor behaviours [5]. Although distinct motor patterns for speech and other oromotor functions (e.g., feeding) begin to develop during infancy, it may also be true that infants with more highly developed oromotor skills early in development (e.g., at 6 months) may also demonstrate more advanced speech development. In other words, a relative strength in one domain may be related to a relative strength in a related domain, and strengths in each area may reflect strong underlying neural integrity that supports development across skills. This relationship is important to understand because feeding difficulties are readily observable early in infancy, often marked by overt symptoms such as coughing, gagging, and inadequate weight gain [7]. In contrast, delays in speech production are usually not detected until after 12–18 months of age, when children are expected to begin communicating verbally. Thus, understanding how infant oromotor skills are related to speech development could inform early identification of infants at‐risk for later speech difficulties.

Infants learn speech initially through producing speech‐like, non‐crying vocalisations called protophones. Protophones include sounds like squeals, vocants (vowel‐like sounds), and growls that show early vocal control and exploration before true speech emerges. Infants produce protophones far more often than cries, starting within the first month of life [8], and therefore protophones are abundant in early development. Protophones constitute the fundamental acoustic–phonetic precursors that underpin both the emergence of vocal categories and the rapid progression of communicative interaction [8]. They also facilitate turn taking in a way that supports language development [9]. Between 3 and 8 months of age, infants begin to produce protophones with increased variety, including production of full vowels and marginal babbling, in which consonant and vowel‐like sounds are combined [10, 11, 12]. Between 6 and 10 months of age, infants begin to produce protophones that sound more like recognisable consonant and vowel sounds [13, 14], which is also around the same time that canonical babbling emerges. Although the protophones produced in canonical babbling are not fully formed consonants and vowels and do not yet carry linguistic meaning, listeners begin to perceive these protophones as distinguishable speech sounds during this stage [14]. Early phonetic development, including the number of consonants infants produce, is positively correlated with later lexical development [15].

The emergence of canonical babbling is an extensively studied and perceptually identifiable speech milestone. Canonical babble refers to production of speech‐like syllables that include at least one consonant and one vowel sound [16]. Canonical babble can include reduplicated babble or productions of multiple, identical consonant–vowel syllables (e.g., “baba”). Babbling in its most advanced form, termed variegated babble, includes syllables with multiple different consonants or vowels (e.g., “bada” and “dagu”). The onset of canonical babbling typically occurs between 5 and 10 months of age [17]. Both direct observation and parental reports, even with minimal training, have been established as reliable methods for identifying the onset of babble emergence [18, 19, 20]. Babble emergence prior to 10 months of age is an important milestone as delayed babble emergence is associated with later speech and language difficulties [21, 22] and with developmental disorders [23]. Delayed canonical babble is a likely marker for later speech and language difficulties [21, 24], making it useful for early detection; however, there is a wide range of variability in babbling production among infants. Further, early vocal development provides a crucial foundation for higher level functions including lexical development [15] and phonological awareness [25]. Phoneme development, including the number of phonemes infants produce, is positively correlated with later lexical development [15].

Early feeding development is also well studied [26]. During the first 6 months of life, infants receive nutrition solely via breastmilk and/or formula and do not require solid food. Six months represents a critical point in development, marking the approximate and recommended transition from consumption of liquids to intake of a combination of liquids and solids [27]. In fact, the American Academy of Paediatrics recommends starting solid foods around 6 months of age for infants as this is when most infants are developmentally ready to safely explore new textures and tastes alongside breastmilk or formula [27]. This critical period for feeding development is also marked by infants' ability to take food from a spoon and manage soft foods that require chewing. These milestones emerge alongside anteroposterior tongue movement for suckling and broader motor developments in trunk and head control for independent sitting while feeding [26]. Thus, 6 months is a key transitional and critical period for infant feeding development.

The Child Oral and Motor Proficiency Scale (ChOMPS) [28] is a valid and reliable caregiver‐report measure designed to assess oromotor, feeding, and gross motor development in infants and children ages 6 months to 7 years [29]. As such, the ChOMPS provides a functional index of oromotor development and has been previously linked to early measures of neuromotor integrity. Recent work from our lab has shown that non‐nutritive sucking (sucking without nutrient delivery) at 3 months of age is associated with later oromotor and general motor skills, as measured by the ChOMPS scores at 12 months, in a cohort of 69 full‐term infants [30]. These results suggest that the ChOMPS is a sensitive measure for capturing differences in oromotor development; however, prior research has not examined associations between ChOMPS scores and measures of early speech development.

Though previous studies indicate connections between early motor and speech development, little is known about the specific relationship between oromotor development, phonetic development (e.g., acquisition of speech sounds), and onset of reduplicated babble in infancy. The current study aimed to determine whether infants' oromotor skills were related to the onset of babbling and the phonetic variety of their consonant and vowel‐like protophones at 6 months of age. We specifically focused on the 6‐month timepoint to capture infants with a relatively early onset of babbling because the onset of canonical babbling is expected to occur between 5 months of age at the earliest and can occur up to age 10 months in typical development [17]. For this study, we were interested in examining whether infants with relatively early vs. later (but typical) emergence of canonical babbling differed in their oromotor skills to determine if developmental strengths in these domains are related. We hypothesized that infants with more advanced oromotor development would also produce a larger variety of consonant and vowel‐like protophones and show relatively early babbling onset.

2. Participants and Methods

2.1. Participants

Participants were a subset of infants and caregivers enrolled in a larger, ongoing longitudinal study examining the relationship between early sucking and motor speech development in full‐term and late‐preterm infants. Study procedures were approved by the Northeastern University Institutional Review Board, and caregivers provided informed consent. Participants were recruited using a convenience sampling approach, including flyers, social media posts, and word of mouth. Preterm infants participated in study sessions at their corrected ages. Infants were excluded from the larger study if they had any caregiver‐reported history of neurologic or chromosomal disorders.

2.2. Data Collection Procedures

Caregivers reported information regarding their infant's babbling and perceived phonetic inventory through an online questionnaire distributed via the REDCap [31] electronic data capture software platform when the infant was 6 months old. Five of the survey questions were developed for this study based on prior, validated methods for use of a caregiver report to document babble emergence [19]. We asked caregivers to report observations of canonical babble, as well as perceived consonant and vowel sounds produced over the past month at home. Specifically, we asked caregivers to provide a “Yes” or “No” response to the question “Does your child say the same syllable several times in a row, like ‘babababa’ or ‘dadada’.” We also asked caregivers to report the speech sounds they had heard their infant produce from a list of early consonants that have been reported in babbling up to 12 months of age [22] (i.e., /m/, /b/, /n/, /w/, /d/, /p/, /h/, /g/, /j/) and vowels representing distinct places of articulation [32, 33] (i.e., “ah” as in “hot,” “oo” as in “boot,” “ee” as in “beet,” and “uh” as in “bug”), selecting all that applied.

Although we did not expect production of fully developed consonant and vowel sounds at 6 months, we aimed to capture the infants' variety of consonant and vowel‐like protophones by asking parents to report the speech sounds they perceived to have heard their infant produce. Parent report is less commonly used to measure the phonetic inventory; however, good alignment between parent ratings and phonetic transcription has been reported for identification of early developing consonants in young children, including stops and nasals [34]. This method has not been validated in infants, but for the purposes of this exploratory analysis, it allowed us to obtain a measure that captured the protophone that parents had heard their infant produce. Importantly, this information was not meant to provide information about specific sounds in the infants' inventory. This measure took approximately 5 min for caregivers to complete. The full text of these questions is included in appendix S1.

To measure oromotor skills, caregivers completed the ChOMPS [28, 29] also using the REDCap platform [31]. The ChOMPS includes 63 items addressing a range of motor behaviours across four subscales, to which caregivers indicate the frequency of their child's performance using a 3‐point scale (“Yes,” “Sometimes,” or “Not Yet”). “Yes” responses are scored as two points; “Sometimes” responses are scored as one point, and “Not Yet” responses are scored as zero points. Subscale scores are summed to yield a total score. The ChOMPS takes approximately 15 min to complete. Although the ChOMPS total score includes questions about gross motor skills, the majority of items pertain specifically to oromotor function, and scale validation is based on the total score.

2.3. Data Analysis

Developmental measures of interest for this analysis included the infant's ChOMPS total score at 6 months, parent‐reported presence of reduplicated babble at 6 months, and parent‐reported number of perceptually distinguishable consonant and vowel‐like protophones the infant produced at 6 months. Descriptive statistics summarise developmental, oromotor, and babbling outcomes across term status (preterm or full term) and overall. The relationship between the presence of babbling at 6 months and CHOMPS score at 6 months was assessed graphically using a boxplot. Linear regression models were used to assess associations between ChOMPS scores at 6 months and babbling outcomes, both continuous (e.g., number of different protophones) and dichotomous (e.g., presence of babbling at 6 months). Crude linear models and models adjusting for term status and sex at birth were fit for both speech outcome measures. Results for continuous outcomes are reported as beta coefficients, and results for binary outcomes are reported as odds ratios. Both estimates are reported with standard errors, p‐values, and 95% confidence intervals. Statistical tests were two‐sided and conducted at the 5% significance level. All analyses were conducted using R (version 4.4.1).

3. Results

A total of 51 infants were included in the study. The sample was balanced by sex (49.02% female; 50.98% male). Note, 57 total infants were enrolled in the larger study at the time of analysis; however, six participants were excluded from all analyses due to missing data. 51 infants were included in the first analysis (ChOMPS scores and number of protophones). Two caregivers did not provide information about the presence of babbling; thus, 49 infants were included in the second analysis (ChOMPS scores and presence of babbling at 6 months). Caregivers provided information about hearing history in the study's intake form, distributed at the time of the online questionnaire. Forty‐eight of the 51 infants passed their newborn hearing screenings, per parent report. The remaining two parents reported their infant's hearing had not been tested but did not endorse any history or symptoms of hearing difficulty.

Caregiver and infant demographics are presented in Table 1. Mean ChOMPS scores, measuring oromotor development at 6 months, were 42.5 (SD = 11.4), with a slightly higher mean in the preterm subgroup (45.4 vs. 42.0). The average number of different protophones perceived by caregivers was 3.83 (SD = 2.89), and the mean age at onset of reduplicated babble was 7.40 months (SD = 1.16), consistent across subgroups.

TABLE 1.

Infant and caregiver demographic information.

	All Infants (50)	Late‐Preterm Infants (9)	Full‐term Infants (42)
Birthweight in pounds (M, SD)	6.78 (1.36)	4.58 (0.79)	7.22 (0.97)*
Gestational age in weeks (M, SD)*	37.81 (2.51)	33.16 (0.69)	38.72 (1.52)*
Post menstrual age in months (M, SD)*	14.84 (1.36)	14.87 (0.97)	14.84 (1.43)*
Female	25 (49.02%)	5 (55.56%)	20 (47.62%)
	Caregivers (51)
Age (years, SD)	35.28 (3.41)
Married	45 (88.24%)
Single	1 (1.96%)
Partnered	5 (9.80%)
Highest level of education in household
College degree or higher	6 (11.76%)
Graduate degree or higher	33 (64.71%)
Doctorate or higher	12 (23.53%)
Race
White	37 (72.55%)
Multiple races	14 (27.45%)

^*Indicates one case of missing data for a full‐term infant.

The adjusted linear regression analysis showed a statistically significant positive association between ChOMPS scores at 6 months and the number of protophones reported, controlling for preterm status and sex (β = 0.12, p < 0.001; Figure 1, Table 2). This model suggests that each 1‐point increase in ChOMPS Score at 6 months is associated with 0.12 more protophones produced (95% confidence interval (CI) 0.061, 0.188). Preterm birth and male sex were not significant predictors in this sample.

FIGURE 1.

Association between Total ChOMPS score and number of different protophones produced at 6 months. n = 51.

TABLE 2.

Associations between child oral and motor proficiency scale (ChOMPS) score and number of phonemes produced at 6 months.

Term	Beta	St. Error	95% Confidence Interval	p‐value
ChOMPS Score	0.12	0.032	(0.06, 0.19)	< 0.001
Preterm status	−0.10	0.98	(−2.07, 1.88)	0.92
Male sex assigned at birth	0.28	0.71	(−1.15, 1.71)	0.69

The adjusted logistic regression models examining the relationship between ChOMPS score at 6 months and presence of babbling at 6 months resulted in statistically significant measures of association. From this model, a 1‐point increase in ChOMPS score was associated with 9.2% higher odds of babbling, controlling for preterm status and sex (OR = 1.092, p = 0.01) (Figure 2, Table 3). Again, preterm status and sex were not significantly associated with babbling outcomes.

FIGURE 2.

Distribution of Total ChOMPS scores at 6 months in infants who were already babbling by 6 months (<= 6 Months) and those who were not yet babbling at 6 months (> 6 Months). n = 49.

TABLE 3.

Associations (Odds Ratios [OR]) between child oral and motor proficiency scale (ChOMPS) score and presence of babbling at 6 months (yes/no).

Term	OR	St. Error	95% Confidence Interval	p‐value
ChOMPS Score	1.09	0.03	(1.03, 1.18)	0.001
Preterm status	2.57	0.85	(0.47, 14.32)	0.27
Male sex assigned at birth	1.13	0.70	(0.28, 4.53)	0.86

4. Discussion

This study aimed to examine relationships between oromotor skills and early speech development at 6 months of age. Results revealed two primary findings: (1) Infants with stronger oromotor skills (as measured by ChOMPS total scores) were reported to produce a wider variety of consonant and vowel‐like protophones compared to infants with lower ChOMPS total scores and (2) infants who were already babbling by 6 months of age had higher ChOMPS total scores, indicating stronger oromotor skills than infants who were not yet babbling. Together, these results support a connection between oromotor development and speech development in infants. These results are discussed in depth below.

In the present study, we used ChOMPS Total scores as an index of oromotor development. This validated parent‐report scale assesses the variety of different oromotor and feeding skills infants are exhibiting and thus provides a functional measure of oromotor development. Six months is the minimum age for administering this scale, and the distribution of scores in our sample reflected an expected range of oromotor skills among infants at this age. Our results showed that ChOMPS total scores were significantly related to the number of different protophones parents reported that their infants produced at 6 months of age, controlling for sex and preterm birth status. As infants' speech systems develop, they begin to produce a wider variety of consonants and vowel sounds, expanding their phonetic inventories. Prior research has shown that larger phonetic inventories in infants are related to stronger language outcomes [35] and, conversely, infants who later develop speech disorders have more limited phonetic inventories in their early vocalisations [36]. Thus, present findings suggest that stronger oromotor skills are associated with more advanced pre‐linguistic speech development at 6 months of age.

Similarly, our results also showed that infants with higher ChOMPS scores are significantly more likely to be “early babblers” (i.e., to already be producing reduplicated babbling at 6 months of age). Because the expected onset of canonical babbling is between 5 and 10 months of age [17], the infants who are already reported to be babbling at six months of age are exhibiting relatively advanced speech development at this timepoint. These findings are consistent with those of previous research indicating that oromotor skills and speech production develop as interacting, related systems [1]. Our findings build on this understanding, indicating that a relative strength in one domain (oromotor development) may co‐occur with a relative strength in another domain (speech production). This is not surprising given reliance on shared musculature [2] and common need for oromotor coordination, planning, and execution [3].

Importantly, our cohort included both full‐term and late preterm infants (tested at their corrected age). Although prior studies have shown that preterm infants are likely to show delays in feeding and speech [36, 37], in the present study, preterm status was not a significant predictor of either the infant's reported number of different consonant and vowel‐like protophones or the likelihood of canonical babbling at 6 months of age. This inconsistency with prior research may be partially explained by the small sample of preterm babies included in this study; group differences may appear with a more balanced sample. In addition, our study included late preterm babies who may be at lower risk for developmental delays than early preterm infants [37]. It is also important to note that ChOMPS scores did not differ between the full‐term and preterm groups in this study. Infant sex was also not a significant predictor of reported protophone inventory or early babbling onset in the present study.

5. Clinical Implications

While childhood speech disorders are identified after babbling and first words emerge, early oromotor difficulties are readily observed in infancy. Our findings show associations between oromotor and early speech development at 6 months of age. Although we could not identify babbling delays at 6 months of age in this sample, results suggest that infants with oromotor weaknesses may be more likely to show delayed babbling—a known risk factor for later speech challenges.

6. Limitations and Future Directions

One limitation of this study is the reliance on caregiver‐reported measures rather than direct observation or standardised clinical assessment, which may introduce reporting bias or limit the accuracy of these data. In particular, the use of parent reporting for measuring the phonetic variety of sounds infants produce has not been validated in 6‐month olds, and using direct observation and coding of infant vocalisations would strengthen future studies. Additionally, the sample included a small number of late preterm infants, which may restrict the generalizability of the findings to this population. Also, the sample included infants from households of relatively high socioeconomic status, as measured by caregiver education level. Future studies incorporating larger, more diverse samples and direct assessment methods will be important to confirm these patterns and explore their implications for the early identification of infants at risk for speech delays. In addition, this study only examined infants at 6 months of age; future research examining longitudinal development of oromotor and speech skills within children is needed to better understand connections between emergence of these skills. Future research should also consider additional factors associated with the onset of babbling, such as the home language environment.

7. Conclusions and Future Directions

Findings from this study suggest a possible link between early oromotor development and emerging speech abilities in infancy. Using caregiver‐reported ChOMPS scores as a proxy for oromotor function, we observed that infants with stronger oromotor skills at 6 months tended to produce a larger variety of consonant and vowel‐like protophones and were more likely to be early babblers. These associations raise the possibility that oromotor and speech systems may develop in tandem, potentially shaped by overlapping neural and muscular pathways. Although preliminary, these results point to the potential value of early oromotor behaviours as indicators of neuromotor development that underlie both feeding and speech. Future research should examine whether infant oromotor scores can predict later babbling and speech skills and identify early markers for speech disorder risk, potentially improving access to early intervention services.

Author Contributions

A. Martens: writing – review and editing, project administration, investigation, supervision, data curation.

Funding

This work was supported by the National Institutes of Health, R01 DC019902. Research reported in this publication was supported by the National Institute on Deafness and Other Communication Disorders of the National Institutes of Health R01 DC019902, PI Zimmerman.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Appendix S1: Questionnaire Items Pertaining to Babble Emergence and Phoneme Production.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.