Using a Sequential Skills Training Model to Increase Oral-Motor Skills for Consuming Table-Textured Foods

Abstract

Children are expected to advance their oral-motor skills through experiences with different types and textures of foods that are gradually changed over time. However, children with pediatric feeding disorder may not go through the same developmental progression of eating, which interrupts the emergence of oral-motor skills that are necessary to transition to higher textured foods without direct instruction. Few published studies have evaluated systematic methods to teach oral-motor skills like tongue lateralization and mastication to children with feeding disorder. Therefore, the purpose of this study was to develop a sequential skills training program that focused on chewing, mastication, tongue lateralization, and mouth clean for a child with pediatric feeding disorder. This training included chewing on a chew tube, mashing crumbles of dissolvable foods, chewing in tulle netting starting with dissolvable foods and progressively moving to table-textured foods, and side placement chewing. At baseline, chewing, mastication, tongue lateralization, and mouth clean did not occur, and all of these behaviors increased after the sequential skills training package. Furthermore, the child successfully consumed table-textured foods at discharge.

Oral-motor skills for feeding begin to develop in utero and are typically completed by age four (Arvedson & Lefton-Greif, 1996). In utero, nonvoluntary reflexes develop usually around 28 to 37 weeks (Delaney & Arvedson, 2008). Therefore, when babies are born prematurely, those reflexes are not fully developed, which may cause delays in oral-motor skills, specifically with feeding. Voluntary reflexes of sucking start to develop from birth to 3 months of age as babies are primarily bottle or breastfed at this time (Meyer, 2000). Thereafter, at 4 to 6 months of age, babies develop better head control and are able to sit upright with support, allowing the jaw and tongue to move forward to support what is known as the munching pattern of chewing and at this point, babies may learn to mash foods. At 6 to 9 months of age, babies begin to eat dissolvable foods, and chewing begins to be more refined with age and experience where the tongue will start to move up and down and side to side when chewing (Delaney & Arvedson, 2008; Stolovitz & Gisel, 1991). During this time, the gag reflex also starts to diminish. By 9 to 12 months of age, tongue lateralization starts to emerge, where the tongue is used to transfer food from side to side in the mouth (Delaney & Arvedson, 2008). At 12 to 18 months of age, chewing becomes more efficient with a mature lateral and rotary chewing pattern, where the jaw moves in a circular motion to masticate (to grind or crush) the food (Stolovitz & Gisel, 1991). Most children are consuming a diet mostly of table-textured food by 24 months of age (Illingworth & Lister, 1964), and oral-motor skills related to chewing are fully developed by 4 to 5 years of age (Schwartz et al., 1984).

Of particular importance to chewing are the skills associated with tongue movement, which are inextricably linked to successful chewing (Le Révérend et al., 2014). The tongue moves food with a lateral side-to-side movement, the upper and lower teeth contact the food until it is sufficiently ground, then the tongue recollects the food to form a bolus, and finally, the tongue lifts the food toward the back of the mouth to be swallowed. In an age-typical eating progression, oral-motor skills follow a sequential progression in which one skill builds on the next. Reaching each milestone is not a result of maturation alone, but the emergence of each oral-motor skill is dependent on the successful practice of a prior skill. Unfortunately, children with feeding disorder may not go through the same developmental progression of eating due to underlying medical complications such as gastroesophageal reflux disease (GERD), constipation, prematurity, sensory sensitivities, or a combination of factors which may cause pain, discomfort, gagging, or vomiting when eating (Patel, 2013).

Alternatively, some children who display food selectivity may also experience oral-motor deficits if they do not progress beyond certain foods, such as dissolvable snacks. For example, children with autism spectrum disorder have been shown to have worse chewing function compared to typically developing peers (Sahan et al., 2021). Regardless of the cause of oral-motor skill deficits, providing sufficient practice opportunities becomes increasingly challenging when inappropriate mealtime behaviors (e.g., head-turning, batting, or blocking) arise. This may eventually result in the loss of previously acquired skills and a failure to acquire new skills because practice is not occurring. Developmentally, the child may remain in a certain stage of eating that is not appropriate for their age, where skills are not progressing as typical, becoming dependent on tube feedings, purees, liquids, or dissolvable snack foods.

Previous research on addressing oral-motor skill deficits has included texture fading (e.g., increasing the food texture from puree to chopped table food). For example, Shore et al. (1998) successfully increased the consumption of table-textured foods by systematically increasing texture incrementally, starting with pureed foods and adding texture over time. However, no chewing or other oral motor data were collected, making it difficult to draw firm conclusions about the possible effects of texture fading on oral-motor skills.

In another study, Eckman et al. (2008) used texture fading, shaping, differential reinforcement, and extinction to increase the consumption of table-textured foods. Although improvements in chewing were observed, it was unclear which, if any, component was responsible for increases in chewing. In addition, mastication and tongue lateralization were not measured, so we cannot be sure if the treatment resulted in improvements in behaviors that are necessary for advancements in chewing.

Another strategy that has been evaluated is 3-step prompting (verbal, model, physical prompting; Volkert et al., 2013) in combination with differential reinforcement and extinction. In this study, the prompting sequence and praise may have been effective at increasing chews per bite because the behavior was already in the participants’ repertoire at baseline, which may be different for children without chewing skills. A notable part of this study was that the authors operationally defined “mastication” (or a by-product of chewing) as a measure of how effective the child was chewing. They were also able to demonstrate an increase in mastication with the same treatment. The authors extended this study by presenting food within a small tube and fading the tube over time for children who did not engage in baseline level of chewing (Volkert et al., 2014). Because the children in this study had a history of swallowing before chewing, the tube with a bite of food was placed directly on the molar to control bite placement. Chews per bite and mastication increased across foods and across participants. It is unclear from Volkert et al., (2013, 2014) studies if tongue lateralization emerged simply with chewing training because these data were not collected.

Adams et al. (2020) focused on teaching tongue lateralization in isolation by using verbal prompts, modeling, differential reinforcement, and extinction when crunchy food was presented in the front of the mouth. Chewing was taught in isolation using the same treatment by placing crunchy food directly on the molars. However, for two participants, both skills needed to be taught together to increase both tongue lateralization and chewing in a coordinated chain. Similarly, Phipps et al. (2023) taught tongue lateralization using a prompting hierarchy, shaping, modeling, differential reinforcement, and extinction. These authors used a Nuk brush to prompt the child to move their tongue if the child did not move the tongue after a model prompt. Chewing and mastication data were not presented; therefore, it is unclear if these exercises led to increases in tongue lateralization needed to consume table-textured foods.

As mentioned previously, children learn the necessary oral-motor skills to consume table-textured foods by experiencing different types and textures of foods (Delaney et al., 2021) rather than exercises alone. Taylor (2020) evaluated a treatment package that included differential reinforcement, redistribution, and extinction to increase chews per bite, starting with easy, dissolvable foods and working toward hard table foods. Although the authors indicated that the child was consuming all table-textured foods after the study, mastication and tongue lateralization data were not presented, so it is unclear if these other skills emerged as a result of this treatment package.

Functional Chewing Training (FuCT) is another treatment approach that has been shown to be effective in increasing chewing skills in children with cerebral palsy and atresia-tracheoesophageal fistula (Arslan et al., 2017, 2020). The FuCT is a holistic approach that focuses on positioning the child, positioning the food, sensory stimulation, chewing exercises, and adjustment of food consistency. Although chewing function increased in a large number of patients using FuCT, the effects of each step on chewing are unclear because data were not collected on specific oral-motor skills but rather based on the Karaduman Chewing Performance Scale (Arslan et al., 2016), which is a rating scale on performance. It is also unclear whether children successfully ate table-textured foods at the conclusion of the study.

Previous chewing research has been limited, and treatments have varied. Additionally, previous research has used varying dependent measures and operational definitions of relevant dependent measures, such as “chew,” which makes comparing the results of these studies difficult. Besides the research on FuCT, previous research has primarily focused on one skill or component to teach when it comes to the chain of chewing. It is unclear if each part of the chain needs to be taught and what steps are needed for the oral-motor skills for chewing to emerge. Therefore, the purpose of this study was to (a) evaluate a sequential skills training model that focuses on the chain of behaviors needed to successfully consume table-textured foods; (b) evaluate all four dependent measures (chewing, tongue lateralization, mastication, and swallowing); and (c) introduce a novel approach to teach the necessary oral-motor skills to eventually consume table-textured foods.

Method

Participant

Seth was a 3-year-old boy who was referred to an intensive home-based interdisciplinary pediatric feeding disorders program by his medical team, which included a gastroenterologist, occupational therapist, and dietician for 100% liquid dependence by mouth and poor weight gain. Seth had a history of prematurity, GERD, sleep apnea, emesis, malrotation (fixed with surgery), and narrow pylorus. Seth had no other developmental diagnosis, and he had previously received occupational therapy for two years to address his feeding difficulties with minimal improvement. His oral motor status was evaluated by his occupational therapist, suggesting that Seth had limited tongue lateralization and chewing skills; however, he was able to safely swallow liquids and pureed foods based on the results of a modified barium swallow study. He was deemed safe by his gastroenterologist and previous speech and language pathologist (SLP) to participate in this study and to receive treatment from the program. Our intensive home-based interdisciplinary program involved behavior analysts, an SLP, and a dietitian. Seth’s existing medical team was informed of his progress on a monthly basis, and further consultation was provided when needed.

Setting and Materials

We conducted all feeding sessions in the patient’s kitchen at their home. We conducted 10–12 sessions per day between 7:30 am–6:30 pm for three consecutive days each month during regularly scheduled meals (breakfast, lunch, snack, and dinner). In between treatment visits, caregivers were trained to implement the training step that Seth was on by the end of the visit, and the caregivers followed that step until the next scheduled visit. The caregivers conducted these sessions as outlined below four times per day before regularly scheduled meals in between physical visits. The data presented in this study were collected during physical visits by the behavior analyst and sessions either conducted by the behavior analyst or a trained caregiver. The behavior analyst always conducted the initial sessions and then role-played with the caregiver; once the caregiver could implement the step with high accuracy, the caregiver conducted sessions as well. Session duration varied depending on the step being conducted and Seth’s performance (between 5 and 20 min), but five trials were conducted for every session because there was no session cap. Seth did not engage in emotional responding, but if that had been the case, a session cap would have been necessary to reduce these behaviors.

Prior to this chewing analysis, a treatment protocol was developed to increase acceptance of pureed foods, as Seth was liquid-dependent upon admission. The goal of introducing purees first was for Seth to go through the developmental progression of eating, which primarily starts with purees. Seth was only able to tolerate thin, smooth purees initially. If presented with thick or textured purees, he would gag and vomit. Therefore, we decided not to take a texture-fading approach but rather teach the necessary oral-motor skills to chew.

During all sessions, Seth sat in a highchair with chest and lap straps and a tray in a 90–90-90 position with his back flat against the back of the chair, his upper thighs resting on the seat of the chair, and his feet supported on the footrest as recommended by the SLP. Other materials included a timer, paper towels, paper and pencils for data collection, and an iPad. Feeding utensils included a chew tube, a Nuk brush, a small maroon spoon, a baby spoon, and tulle netting. The tulle netting was cut into 4 in × 4 in squares, and it was washed with water and bottle cleaner and dried before use. A small rubber band was available to ensure that the food remained in the netting if needed. A new one was used for each trial.

The target food was apple, which was presented in ¼ in x ¼ in pieces during all baseline and brief reversal sessions. This food was selected to maximize the effectiveness of chewing training as it was observed that Seth would independently put bites of apple in his mouth but would not chew or swallow; rather, he would move the apple around in his mouth in a sucking motion and then spit it out. The family had never seen Seth prematurely swallow any food (i.e., swallow a piece whole without chewing), and we selected a size that would mitigate any concerns in the event of early swallows. Importantly, the behavior analyst conducting these sessions was also CPR-trained for infants and toddlers, and we strongly encourage other researchers to establish these safeguards.

During the crumble condition (described below), a dissolvable tea biscuit was used. During subsequent conditions, initially, the tea biscuit was used, and then a variety of dissolvable foods such as puffs and crackers were presented. These dissolvable foods were used according to Taylor (2020). During the table-textured condition, a variety of table-textured foods were presented, excluding the apple, as that food continued to be the baseline food.

During the study, the caregivers did not introduce new foods. They continued to practice the foods the behavior analyst worked on during the physical visits. However, once the study was concluded, we provided the caregivers with a protocol on how and when to introduce new foods. Our dietitian monitored his diet, and we continued to introduce table-textured foods in all food groups so he met his nutritional needs during the study and at discharge.

Feeders and Observers

The behavior analyst was a masters-level Board Certified Behavior Analyst. The behavior analyst or trained caregiver conducted all sessions. Although caregiver training was beyond the scope of this study and will not be discussed in detail, the behavior analyst did train all caregivers at the conclusion of each treatment visit to carry out the training step between physical visits with at least 80% accuracy.

Response Measurement and Interobserver Agreement

The primary dependent variables were chew, tongue lateralization, mastication, and mouth cleans. All dependent measures were scored as occurrence or nonoccurrence for each bite and then converted into a percentage for each session, with the exception of chew. Chew was scored as a frequency by counting the total chews that occurred during the session and dividing by total bite presentations for each session to obtain chews per bite.

The observer scored a chew each time they observed one up-and-down motion of the jaw of at least 1 cm while food was visible on the molar following the verbal prompt to chew. The observer scored tongue lateralization after observing initial sideways movement of the tongue of at least 1 cm in which the tongue touched the inner cheek or corner of lips independently or after a verbal prompt after the bite was deposited. Tongue lateralization was not scored if the tongue protruded outside the lips or after a model prompt. Tongue lateralization was only scored during conditions in which the feeder targeted tongue lateralization; that is, if tongue lateralization was not required to complete the step, the observer did not record tongue lateralization (e.g., side placement conditions). The observer scored mastication when they observed food to be chewed to the texture of minced garlic after 10 chews or 15 s after acceptance, whichever came first. This was not scored during side placement strip because the strip was being moved into the mouth to ensure mastication rather than it occurring independently, as was the case with the prior steps. The observer scored mouth clean (swallowing) when there was no visible food, the size of a pea or greater, in the mouth 30 s after mastication. Mouth clean was only scored for the steps that required swallowing. Although swallowing occurred for crumbles, mouth cleans were not scored because the focus of this step was on mashing rather than swallowing, and only a small amount of food was deposited. Data were also collected on inappropriate mealtime behaviors, acceptance, and gagging, but they were not the primary dependent variables used to make phase changes, and therefore, data will not be presented.

A second data collector, either a BCBA-D or BCBA, scored videotaped sessions for 11% of randomly selected sessions. Although we would have preferred to calculate interobserver agreement (IOA) for a larger percentage of sessions, this was not possible due to circumstances. However, Hausman et al. (2022) indicated that the number of sessions with IOA may not be as important as the consistency of the data, which we did obtain in this study. The high-resolution video camera attached to a computer was placed on a table in front of Seth, next to the feeder, so that all behaviors could be captured. IOA was calculated by dividing the number of agreements by the total number of agreements plus disagreements multiplied by 100 for mastication, tongue lateralization, and mouth clean. We defined an agreement as both observers scoring the behavior occurred or did not occur for that trial, and a disagreement as one observer scoring and one observer not scoring the behavior in that trial. For chews per bite, we calculated total count IOA by dividing the smaller count by the larger count and multiplied by 100. Mean interobserver agreement was 92% (range, 60–100%) for chew, 93% (range, 80–100%) for tongue lateralization, 95% (range, 80–100%) for mastication, and 100% for mouth clean.

Treatment Integrity

Treatment integrity data were collected from videotaped sessions for 11% of randomly selected sessions. A 9-item checklist identifying each component of the procedures was developed and filled out by the second observer. Treatment integrity was calculated by dividing the number of correctly implemented steps by the total number of steps. If a specific step did not apply for that session, then it was not included in the denominator. Mean treatment integrity was 95% (range, 88–100%) across baseline and training sessions for the behavior analyst and 88% (range, 83–100%) for caregiver-conducted sessions.

Experimental Design

We used a brief reversal design to evaluate the efficacy of the treatment and whether subsequent steps were necessary. The behavior analyst conducted a baseline probe (using apple only) after Seth had mastered each treatment step prior to starting the next step.

This study was conducted in the context of Seth’s clinical care during the novel coronavirus (COVID-19) pandemic. Therefore, it was challenging to collect data on all dependent and independent variables because we were trying to be as efficient as possible considering the uncertainty we faced during the pandemic. In addition, with the nature of our treatment program including monthly physical visits, it was impossible to have the level of control over extraneous variables that is present in clinic and hospital-based programs as this study occurred in Seth’s typical environment. IOA was also more challenging because it can only be obtained by videotaped sessions, and in this study, only a small percentage of sessions were videotaped owing to challenges with COVID-19.

General Procedure

Across all conditions, the behavior analyst or caregiver conducted 5-bite sessions using nonremoval and differential reinforcement for alternative behaviors (DRA) with the iPad. The caregiver deemed the iPad preferred, and it was restricted to mealtimes only. The iPad was delivered for 30 s after Seth engaged in the target response for each step (see below). Prior to each meal block, the feeder washed their hands thoroughly with soap and water; gloves were not used owing to Seth’s fear of gloves. The feeder presented the bite or utensil and said, “Open ahh,” while holding the bite or utensil at Seth’s lip until he opened his mouth. If he did not open his mouth to accept the bite or utensil within 5 s, the feeder repeated the prompt “open ahh” and modeled a wide, open mouth. The feeder repeated this prompt approximately every 5 to 10 s until Seth opened his mouth to accept the bite or utensil. It was critical that the utensil or food entered the mouth so teaching could take place; therefore, the feeder repeated the prompt and waited until Seth opened. If Seth accepted the bite or utensil within 5 s of the presentation, the feeder provided praise (e.g., “Great job, Seth, good taking your bite!”). There were no differential consequences for inappropriate mealtime behavior, and the feeder continued to keep the bite or utensil at Seth’s lip regardless of inappropriate mealtime behavior until the bite or utensil was accepted. The bite was never removed and remained at the lips until it could be deposited so skills could be adequately assessed. The feeder followed Seth’s head with the utensil or food; however, it was never deposited until he independently opened his mouth. Expelled bites were represented to Seth’s lip as quickly as possible except during baseline. Any chews were counted out loud across all conditions (e.g., “1, 2, 3…”).

Baseline

The feeder presented one bite of apple on the tray in front of Seth in a self-feeder format. If Seth did not take the bite within 5 s, the feeder picked up the bite and presented the bite to Seth’s lips. The feeder presented a new bite every 30 s until five bites were presented. The feeder conducted a mastication check, similar to the mouth clean check described below, 15 s after the bite was deposited or after 10 chews were observed, whichever came first. These criteria were selected on the basis of our clinical experience working with other patients. There are no data-based criteria in the literature at this time, but it is important to note that depending on the food, it may take more or less chews per bite or more or less time to masticate the food. We were able to observe all behaviors because Seth cooperated at some point in the prompting sequence. It is critical that before chewing training is initiated, the child cooperates with a request to check for mastication and mouth clean so accurate data can be collected. If the bite was not masticated, we removed the bite after 15 s more (i.e., 30 s after the bite deposit). If the bite was masticated, we conducted a mouth clean check 30 s after the bite was masticated by saying, “Show me.” If Seth did not open his mouth to show an empty mouth, then a spoon was placed at the corner of the mouth to prompt an open mouth. If he still would not open, the spoon would have remained at the corner of his mouth until he opened, with a “show me” prompt every 15 s. However, this did not occur because Seth would always open once the spoon touched the corner of his mouth. If Seth swallowed (lips closed and observed throat movement) the masticated bite at or before the mouth clean check, a “show me” prompt was delivered early. If his mouth was clean, praise was delivered, and the next bite was presented. If mastication was not observed but a clean mouth was displayed, no verbal praise was delivered because this meant that the bite was swallowed early (without adequate chewing). If the bite was still in the mouth (packed) at 30 s, then the bite was removed. If the bite was expelled, it was not represented, and the next bite was presented after 30 s.

It is important to note that only two baseline sessions were conducted initially because this treatment evaluation was conducted during Seth’s clinical care and was not conducted for research. Also, because it was conducted during COVID-19, we wanted to be as efficient as possible. As discussed by Smith et al. (2022), the number of data points within each phase may become irrelevant due to the large number of data points across phases, and it is unlikely that an extraneous variable would cause the change in the dependent variable. Baseline probes were also conducted at the beginning of most new training steps to determine if further training was necessary. Owing to time constraints, we could not conduct multiple baseline probe sessions more often.

Sequential Chewing Skills Training

Chewing skills training consisted of exposing Seth to a set of treatment components that focused on increasing oral motor skills relating to the chain of chewing and swallowing. For each step, the feeder used 3-step prompting, which consisted of a verbal, model, and physical prompt (if applicable), similar to Volkert et al., (2013, 2014). Seth primarily responded after a model prompt and rarely required a physical prompt. All chewing skills training sessions were five trials or bites. The data were visually analyzed to determine when the next step would be implemented, typically after the caregivers had at least a month to work on the specific step in between physical visits. Once the behavior analyst returned for the next physical visit, she collected data on the step the family was working on and then decided to continue with that step or conduct a baseline probe and proceed with the next step based on the data.

Chew Tube. The feeder presented the red chew tube (see Fig. 1) to Seth’s lip and said, “Open ahh.” This was similar to what was used in FuCT (Arslan et al., 2017). After Seth opened his mouth, the feeder placed the long part of the chew tube on his bottom molars at a right angle and said, “Chew,” while the long part of the tube touched the side of the tongue. The feeder counted correct chews aloud. After three consecutive chews on one side of Seth’s mouth, the feeder moved the tube to the opposite molars on the other side of Seth’s mouth and said, “Chew.” After three more correct chews, the feeder removed the tube and provided praise and the iPad. The iPad was given for 30 s. One trial consisted of a repetition of six total chews. The purpose of this step was to get the verbal prompt “chew” under instructional control and to increase chews.

Fig. 1.

Chew tube. Note: Red chew tube used for the step of training

Chew Tube with Tongue Lateralization. This condition was identical to the chew tube condition; however, after three chews on one molar, the feeder prompted “move it over” and gently depressed the chew tube on Seth’s tongue, starting at the side and began moving the tube to the opposite molar slowly while his tongue followed (see Fig. 2). If Seth’s tongue did not move with the tube, the feeder said, “Try again,” placed the tube back over the molar, and repeated the same instruction while providing a model prompt for tongue movement. If no tongue movement occurred, the feeder moved the tube across Seth’s tongue and depressed on the tongue but did not provide praise. The purpose of this step was to get the prompt “move it over” under instructional control and increase tongue lateralization.

Fig. 2.

Chew tube with tongue lateralization. Note: Red chew tube with tongue lateralization used for the second step of training

Crumbles on Nuk. This condition consisted of taking a dissolvable food and crushing it until it reached the texture of fine grain sand to make crumbles (see Fig. 3). The feeder took the Nuk brush and made it slightly wet by dipping it into water and coating one side of the brush in the crumbles so the crumbles would stick to the Nuk brush. The feeder presented the Nuk to Seth’s lips and said, “Open ahh.” After Seth opened his mouth, the feeder deposited the Nuk in Seth’s cheek using a rolling motion from top to bottom to deposit the crumbles in his cheek. The feeder alternated the side they deposited crumbles on for each trial. After depositing the crumbles, the feeder immediately prompted, “Move your tongue.” This verbal prompt was used because the crumbles dispersed everywhere in the mouth, and there was not simply one piece to move over, as was the case in subsequent steps where the prompt was “move it over.” If Seth lateralized his tongue after the prompt, the feeder provided praise and the iPad. If he did not move his tongue within 3 s, the feeder repeated the prompt and modeled tongue lateralization. If Seth never lateralized his tongue prior to the crumbles melting, the feeder would not have provided the iPad; however, this did not occur. The Nuk was used initially to better facilitate tongue lateralization since it could be rolled across the tongue as opposed to starting with a spoon. The crumbles typically melted within 10 s either by movement of the tongue or just sitting in the mouth due to it being an easily dissolvable food. The feeder checked to make sure Seth’s mouth was clear prior to the presentation of the next bite. However, if any specs of crumble remained in the mouth, a verbal prompt to “swallow” would have been delivered. As there was such a small amount of crumbles on the Nuk, mouth-clean data were not collected. The purpose of the crumbles on the Nuk step was to further increase tongue lateralization and desensitize the mouth to food because Seth had a history of gagging with any texture that would stick to his tongue. The goal was to teach Seth to move his tongue when the crumbles were deposited to prevent gagging.

Fig. 3.

Crumbles on Nuk. Note: Nuk brush with crumbles used for the third step of training

Crumbles on Spoon. This condition was identical to the crumbles on Nuk condition; however, the crumbles were presented on a small maroon spoon (see Fig. 4). The feeder presented the same amount that was presented on the Nuk in the previous condition, which was about a ½ level small maroon spoon. After the bite was deposited, the feeder prompted “mash.” If Seth started to mash the crumbles (one up-and-down movement of the jaw without the use of the teeth or pushing of the food up and down with the tongue), praise and the iPad were delivered. If no movement was observed within 3 s, the feeder repeated the instruction and modeled a mashing movement. If the crumbles had melted and Seth had never mashed, the feeder would not have provided the iPad; however, this did not occur. The purpose of this step was to get the prompt “mash” under instructional control and to further desensitize the mouth with food deposited on the tongue. Although the terminal goal was not to have Seth mash but rather chew, developmentally, babies learn to mash foods before they learn to chew foods. In addition, Seth’s history of gagging on any texture led us to develop this interim step prior to teaching chewing. Further, mashing may be required once the bite has been masticated and ready for bolus formation and swallowing.

Fig. 4.

Crumbles on spoon. Note: Half level spoonful of crumbles on a small maroon spoon used for the fourth step of training

Netting with Dissolvable Foods. In this condition, the feeder wrapped a piece of dissolvable food (1-inch piece) in tulle netting and held it at the binding (see Fig. 5). The feeder held the bite up to Seth’s lip and said, “Open ahh.” After Seth opened his mouth, the feeder placed the bite over his molar while holding the netting at the binding. The feeder alternated the side of Seth’s mouth the bite in netting was presented for each trial. The feeder prompted “chew” and counted each chew out loud. After 10 chews or 15 s, the feeder checked the bite for mastication by removing it from Seth’s mouth and opening the netting. If the bite was masticated, the feeder provided praise and the iPad. If the bite was not chewed up, the feeder said, “We need to keep chewing!” and presented the bite for three more chews and then checked the bite again for mastication. The feeder repeated presenting the bite for three more chews and checking for mastication until the bite was masticated. Tongue lateralization was not scored during this condition since the food was already placed on the molars, and it was not specifically targeted. The purpose of this step was to teach Seth to chew food without it coming out into his mouth. The holes of the netting were not big enough for pieces of food to easily come out. The netting was replaced after each bite presentation (new net for each bite), and the end of the pouch was bound (by twisting or a rubber band) so food could not come out of the other side. Pieces of tulle did not break off and fall out into the mouth because it was durable.

Fig. 5.

Netting with dissolvable foods. Note: Dissolvable food wrapped in netting used for the fifth step of training

Netting with Table-Texture Food. This condition was similar to the netting with dissolvable foods condition, with two exceptions. Instead of dissolvable food presented in netting, the feeder presented table-textured food in the netting (see Fig. 6). The feeder started with mashable foods and then presented harder foods, as described by Taylor (2020). Also, after three chews on one molar, the feeder prompted, “Move it over,” and touched the netting to Seth’s tongue and began moving the food in netting to the opposite molar slowly while his tongue followed. All other tongue lateralization prompts were identical to the chew tube with tongue lateralization condition. The feeder kept moving the food to the opposite side after three chews until the mastication check. If the food was not masticated, then the feeder continued. A new bite was placed in a new piece of netting for the next trial after the previous bite was chewed up. The purpose of this step was to teach Seth to chew more challenging food without it coming into his mouth.

Fig. 6.

Netting with table-texture food. Note: Table-texture food wrapped in netting used for the sixth step of training

Side Placement Dissolvable Strip. The feeder cut a dissolvable food, so it was approximately 1 inch long; the width varied depending on the food used (see Fig. 7). The feeder presented the food to the lips and said, “Open ahh.” After Seth opened his mouth, the feeder placed one end of the strip over the molar at a right angle (similar to the chew tube) and said, “Chew.” The feeder counted each chew out loud. As Seth chewed, the feeder slowly moved the strip into the mouth so he could continue chewing the piece. The strip was moved after every chew response. The feeder continued moving the strip into the mouth and counting chews until the entire strip was deposited and fully masticated. Side placement was done in a way similar to what was discussed in FuCT (Arslan et al., 2017) and Taylor (2020). The purpose of this step was to further increase tongue lateralization.

Fig. 7.

Side placement dissolvable strip. Note: Dissolvable strip of food used for the seventh step of training

Side Placement Dissolvable Loose Piece. This condition was identical to the side placement dissolvable strip condition with the following exceptions (see Fig. 8). The size of the bite was the same at the apple ¼ inch x ¼ inch initially, and then the bites were increased over time. The feeder deposited the piece on the molar and did not hold the bite in place. The feeder also checked for mouth clean 30 s after mastication, and if the bite was swallowed, the feeder provided access to the iPad. If the feeder could see that Seth had swallowed prior to the 30 s check, the iPad was provided at that time. If the bite was packed at the mouth clean check, then a verbal prompt to “swallow” was delivered. This prompt was provided every 15 s until the bite was swallowed. Sessions were never terminated on packing, but it is important to note that mouth cleans were high, and packing rarely occurred. The purpose of this step was to increase chewing with dissolvable foods while requiring limited tongue lateralization due to the food being deposited on the side.

Fig. 8.

Side placement dissolvable loose piece. Note: Dissolvable piece of food used for the eighth step of training

Side Placement Piece with Manual Hold. Owing to a decrease in mastication, the feeder added a manual hold to the side placement piece condition to keep the bite in place on the molar while chewing (see Fig. 9). During this condition, the feeder deposited the bite on the molar with the index finger and thumb and held the bite between the teeth with the index finger only until the bite was masticated. Because the finger was placed in between the cheeks and teeth, Seth was still able to chew the food while the finger was in the mouth. As mastication increased, this prompt was faded by slowly removing the finger from his mouth after three chews, then eventually removing it after fewer chews, and then just putting it on the outside of the cheeks.

Fig. 9.

Side placement piece with manual hold. Note: Dissolvable piece of food with manual hold used for the nineth step of training

Front Placement Dissolvable Food. This condition was identical to the side placement dissolvable loose piece condition, but the bite was deposited in the front of the mouth as opposed to on the molar. If Seth did not move the bite to his molars within 3 s, the feeder prompted, “Move it over.” If he still did not move the bite to his molars within 3 s, the feeder repeated the instruction and modeled tongue lateralization. Finally, if Seth still did not move the bite over within 3 s of the model, the feeder moved the bite to the molar with the Nuk brush. After Seth’s performance was consistent with easier dissolvable foods, such as Trader Joe’s veggie sticks, harder dissolvables, such as pretzel and tortilla chip, were presented. The purpose of this step was to teach both tongue lateralization and chewing of food when presented in a typical format as opposed to side placement (Taylor, 2020).

Front Placement Table-Texture. This condition was identical to the front placement dissolvable food condition, but a variety of table-texture foods were presented across sessions, starting with mashable foods and then moving to harder foods as described by Taylor (2020; see Fig. 10).

Fig. 10.

Front placement table-texture food. Note: Front placement of table-texture food used for the final step of training

Follow-up. The behavior analyst worked on increasing the volume of table-textured food presented during regular meals and provided recommendations to the caregiver. Meals at this point were volume-based rather than bite-based. This was done clinically, and data were not collected during regular meals. However, for the 9-month follow-up sessions, the behavior analyst collected data during the first five bites of a regular meal. During these sessions, formal mastication checks were not done, and mouth cleans were determined when Seth opened his mouth to accept the next bite. Each month, we focused on progressing to age-typical eating by increasing the bite size, increasing the number of bites presented at one time, introducing novel foods, and also eliminating all prompts. Four months after concluding this study, Seth was consuming near-age typical portions of his food independently (e.g., ½ roti, 1 egg, ½ cup pasta) but was still meeting some caloric needs with natural purees (applesauce and yogurt) or liquids. The family was vegetarian, so most of the foods they ate were soft in nature. However, he was able to chew and swallow more challenging textures such as pizza, grilled cheese, and quesadilla.

Results

Chews per bite are depicted in Fig. 11. In baseline, chews per bite were at 0 but increased during the chew tube condition (M = 6). Chewing was not required during the crumbles condition; therefore, no data points are depicted. Chews per bite again increased during the netting condition (M = 8). Chews per bite initially decreased with side placement dissolvable strip but then increased and stabilized (M = 5). Chews per bite continued to be high with side placement dissolvable loose piece (M = 6). Chews per bite increased with front placement dissolvable food (M = 10) and continued to be high during the front placement table texture condition (M = 9). Initially, during baseline probes, chews per bite remained at 0 after side placement dissolvable food in pieces was introduced. Thereafter, chews per bite continued to increase in subsequent conditions during the baseline probe, eventually reaching levels similar to those of the training conditions. Chews per bite increased during follow-up, but this may be due to the type of food presented and bite size, as these data were collected during a typical meal where he self-fed larger bite sizes.

Fig. 11.

Chews per bite. Note: Chews per bite for the treatment evaluation

Data for the percentage of trials with tongue lateralization are depicted in Fig. 12. Tongue lateralization was at 0 during baseline; however, tongue lateralization increased and remained high when it was targeted during the chew tube condition (M = 73%). Tongue lateralization increased during the crumbles conditions (M = 89%) and continued to be at 100% during netting conditions. Tongue lateralization was not scored during side placement conditions because the food was already placed on the molars and did not require tongue lateralization to move the food. Tongue lateralization continued to be high for the front placement condition (M = 94%). During baseline probes, tongue lateralization initially remained at 0; however, tongue lateralization started to increase during the side placement dissolvable loose piece condition, similar to when chews per bite increased. Further, tongue lateralization increased to 100% during subsequent baseline probes and continued to be at 100% during follow-up.

Fig. 12.

Percentage of trials with tongue lateralization. Note: Percentage of trials with tongue lateralization for the treatment evaluation

Data for the percentage of trials with mastication are displayed in Fig. 13. Mastication was at 0 during baseline. Mastication data are not depicted for chew tube and crumbles because mastication was not required for those conditions. Mastication increased when it was targeted in the netting phase (M = 99%). Mastication data were not collected for side placement dissolvable food in strips because the food was fed into the mouth, so mastication occurred as a result of the presentation method. Mastication initially decreased with side placement dissolvable loose piece (M = 60%); therefore, a manual hold was implemented. After the manual hold was implemented, mastication increased (M = 92%). Mastication continued to be high for front placement, with the exception of a few lower data points (M = 92%). During baseline probes, mastication continued to be at 0, but it started to increase after the front placement dissolvable food condition and was at 100% during the last baseline probe.

Fig. 13.

Percentage of trials with mastication. Note: Percentage of trials with mastication for the treatment evaluation

Data on mouth cleans are displayed in Fig. 14. Mouth cleans were recorded for all baseline, side placement, and front placement conditions; that is, mouth cleans were not recorded during chew tube, crumbles, or netting conditions. During baseline probes, mouth clean remained at 0 until the front placement condition, where we observed a slight increase in mouth clean. However, mouth cleans remained high (M = 100%) during front placement condition. Mouth cleans decreased during follow-up; however, this may have been due to bite size and pacing because he often put another bite into his mouth when he had a small amount left from the previous bite. Mouth cleans were difficult to observe as this was during a typical self-fed meal.

Fig. 14.

Percentage of trials with mouth clean. Note: Percentage of trials with mouth clean for the treatment evaluation

Discussion

This study outlined a sequential skills training program to increase chewing, tongue lateralization, mastication, and mouth clean for a child who did not exhibit the oral-motor skills necessary to consume table-textured foods prior to treatment. Exposure to this training program produced increases in chews per bite, tongue lateralization, mastication, and mouth cleans. This is the only study to our knowledge that has evaluated these dependent measures in tandem when teaching chewing.

Given that we saw the largest increases in both chewing and tongue lateralization after presenting bites on the side, side placement of food may be critical for achieving meaningful oral motor outcomes. Other researchers have also shown the efficacy of presenting foods using side placement (Adams et al., 2020; Arslan et al., 2017; Taylor, 2020; Volkert et al., 2014); however, it is unclear from previous studies and the current investigation if side placement alone would be sufficient to increase chewing, tongue lateralization, and mastication. Future researchers could further evaluate whether these behaviors naturally occur over time after placing food on the side or if additional steps are necessary.

Additionally, the number of steps needed and the step to begin teaching may be different for each child depending on their specific oral motor history. This treatment package was composed of many steps, all of which may not be necessary for each child. For example, Seth had a history of gagging with any texture, hence the addition of crumbles. However, for a child who has mashing skills, maybe that step would not be warranted. Further, if a child displayed skills in chewing and masticating dissolvable foods, then steps involving dissolvable foods could be bypassed. Future researchers may want to isolate steps to determine which ones are sufficient and necessary to build the proper oral-motor skills to consume table-textured food for each individual child based on their unique skills during baseline. Although the Karaduman Chewing Performance Scale can determine some level of baseline chewing skills, it does not provide data on specific dependent measures; therefore, it is unclear what steps are needed for training for each individual child.

Another noteworthy contribution of this study was the implementation of tulle netting, where the child was able to chew and masticate the food without pieces of food coming out into the mouth. Anecdotally, free-flowing food can be overwhelming for a child who lacks the proper oral motor skills to consume table-textured foods, which could, in turn, lead to behaviors such as expulsion (spitting out food), packing (holding food in the mouth), or premature swallowing without chewing which can be a choking hazard. Using tulle netting allowed Seth to taste the food and learn an interim step (i.e., chewing) before he was required to also lateralize and swallow the food. It is likely that this step helped minimize Seth's expulsions because he learned to chew and masticate food without having the opportunity to expel it because the feeder held the food through the netting. Although he had a history of expulsion with table-textured foods, expulsions were no longer problematic once he acquired the necessary skills through chewing skills training. In the Volkert et al. (2014) study, they used a plastic tube to hold the food while teaching chewing; however, it may be difficult to keep the food in the tube in the correct position logistically as the piece could fall out of the tube. Furthermore, the child would be chewing on the thick tube and food, which may not mimic the sensation of chewing the food. The tulle netting allowed the feeder more control of the food, easily moving the food from side to side without it falling out, making it possible to also target tongue lateralization. In addition, the tulle netting was flexible (can be cut in any size and shape) and can be wrapped on any food. Further, a new piece of netting can be used for every presentation to ensure consistency, which may not be economical when using commercially available chewing bags.

Although positive outcomes were achieved, there are limitations to this study. Owing to our treatment model of three visits per month, parents served as feeders between visits. The parents conducted sessions on that specific step for a month before the behavior analyst returned for visits, but the parents did not collect data during that time. As a result, it is unclear how much practice was necessary to reach these outcomes. The current study was concluded in 4 months, but the time spent practicing each step varied depending on the mastery criteria and the amount of time between visits. Future studies should control for time so it is clear how much practice a child may need at each step before treatment outcomes are achieved. Also, it is important to note that it took another 4 months after the study concluded to get Seth to eat an age-appropriate portion of table-textured foods for all meals. Although Seth acquired all the oral-motor skills necessary to consume table-textured foods, we observed that his latency to mouth clean increased during typical meals as the portion size increased, potentially as a result of fatigue.

In some cases, a child may only lateralize the food to one side of the mouth and chew primarily on that same side. Anecdotally, it appeared that Seth chewed primarily on one side of his mouth during regular meals; however, when verbally prompted, he was able to move the food to the other side with his tongue. Future researchers may want to collect data on the side of the mouth that is used for lateralization and chewing so all deficits can be identified. If the food is being masticated and swallowed in a timely manner, lateralizing to and chewing on only one side may not be an immediate problem. However, because the goal is for the child to eat an age-appropriate portion of table-textured foods, lateralizing and chewing on one side could pose long-term problems, as we observed with Seth. For example, fatigue may set in, and mastication and swallowing could be compromised later in a meal. Future researchers should evaluate oral-motor skills during typical meals, rather than just five bite sessions, to determine if the duration to mouth clean increases due to fatigue as the meal progresses.

Another limitation of this study is that we only looked at one dimension of tongue lateralization (i.e., initial tongue lateralization) as opposed to the many different ways tongue lateralization impacts chewing. Future research should continue to evaluate the importance of tongue lateralization as it relates to chewing and swallowing food. For example, the tongue is responsible for initially moving the food to the molars, keeping food on the molars until it is properly ground, regathering food to form a bolus, and then lifting for swallowing. Future researchers may want to operationally define tongue lateralization at each point in the chain separately to capture the different nuances and to look at each of these and how they impact oral motor development. Although data were not collected on these different nuances of tongue lateralization for Seth, he learned to lateralize his tongue in these different ways by only being taught side-to-side tongue lateralization. This may not be the case for other children, and each component of tongue lateralization may have to be taught directly.

Future researchers should continue to refine the methodology used to evaluate the efficacy of oral-motor skill interventions. Volkert et al., (2013, 2014) used a multiple baseline across foods to demonstrate experimental control; however, this may not be the best design to evaluate treatments for skill development. One would assume that once a skill is taught, then it would generalize to all foods; however, it only occurred for one food in the Volkert et al. (2013) study. Therefore, was the participant’s performance then related to a motivation deficit rather than a skill deficit? Theoretically, if a skill is taught, it should be displayed with all foods unless motivation to eat the other foods is lacking. At that point, preference for foods should also be assessed to determine what is, in fact, associated with a skill deficit or motivation. In Volkert et al., (2013, 2014), each food had to go through treatment, which can be costly and time-prohibitive. In the current study, we used a brief reversal design to demonstrate experimental control, but it is unclear whether treatment gains were solely a result of the treatment package because this was not replicated with other children, and ultimately, performance increased during baseline probes. However, in the current study, each individual food did not have to go through treatment; rather, generalization of skills occurred for a variety of foods, hence supporting a skill deficit explanation rather than motivation. It is likely that shaping and differential reinforcement during each step resulted in increases in chewing, tongue lateralization, and mastication, which eventually led to a transfer of stimulus control to other foods. Further, this training could also be conceptualized as a manipulation of response effort. The training started with presumably a less effortful response, which was the chew stick, which was paired with reinforcement and then transferred over to more effortful steps (e.g., chewing on food first in netting, then without netting). Future researchers may want to determine the best methodology to use to evaluate an oral-motor skills training program that facilitates both generalization and maintenance and to evaluate the mechanism responsible for behavior change. Future researchers may also want to explore machine learning or other technology to better collect data because it is often difficult to score certain behaviors that occur inside the mouth and are not visible to a human data collector.

The sequential chewing skills training program evaluated in this study was efficacious at increasing chewing, tongue lateralization, mastication, and mouth clean for a child with pediatric feeding disorders, liquid dependence, and oral-motor skill deficits. Future studies should try to replicate this with more children. Although only one child went through this study, we were able to develop a novel sequence of oral motor exercises that simulated a developmental progression. In addition, tulle netting was an innovative addition to the literature to teach chewing to a child with no baseline oral-motor skills. Clinically, we use this same sequence of steps for the patients in our program; however, it must be evaluated more systematically to better understand the mechanisms responsible for behavior change. In conclusion, this is a method that can be safely implemented by trained clinicians who work within an interdisciplinary team.

Author Contributions

All authors contributed to the design and execution of the study. In addition, authors contributed to the writing process.

Funding

The authors did not receive any direct funding for this research project; however, these data were collected within the patient’s clinical care.

Data Availability

All data collected for this study are presented in the manuscript. The excel file where the data are stored can be available upon request.

Consent to Participate

Written informed consent was obtained by legal guardian to participate in research and publication. Statements and Declarations: There are no financial and non-financial interest to disclose from this study. However, the first author of this study is on the Editorial Board for the journal.

Conflict of Interest

The authors of this study have clinical responsibilities; however, promotions are not based on publication records. The first author also has an adjunct faculty appointment, but reappointment is not based solely on publication records. The first author of this study is on the Editorial Board for the journal.