Development of Feeding Cues during Infancy and Toddlerhood

Sample

In the Infant Care study, first time non-Hispanic Black mothers aged 18-35 years and their 3-month-old infants were recruited through the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) clinics in North Carolina and assessed during in-home visits at infant age 3, 6, 9, 12, and 18 months. A total of 217 mothers and infants were recruited at baseline (at infant age 3 months). Mothers had to be willing to participate in home visits and assessments and have healthy infants >35 weeks’ gestation. Infants with Down syndrome, epilepsy, cleft lip or palate, cerebral palsy, failure to thrive, mental retardation, severe food allergies or any condition that might affect appetite, feeding or growth were excluded.

Of the original 217 dyads, 125 had complete video-recorded feeding observation data at 18 months. Stratified purposeful subsamples of mother-infant dyads with the 15 highest, 15 middle, and 15 lowest infant BMI Z-scores (N = 45 dyads) based on the score distribution at 18 months were selected to distinguish patterns of maternal feeding responsiveness among groups based on infant weight at 18 months of age. The BMI-Z score is a statistical measure of the relationship of an infant’s BMI compared to the mean BMI of the total 125 infants who were eligible for this study. Analysis of feeding cues at all time points was performed for the 45 dyads that were included.

Feeding Cues

Infant Feeding Cues were assessed using items from the Responsiveness to Child Feeding Cues Scale (RCFCS), which was developed to measure observed feeding interaction quality during infancy and toddlerhood (Hodges et al., 2013). The RCFCS is based on attachment theory (Ainsworth & Bell, 1969; Bowlby, 1969; Lamb & Easterbrooks, 1981) and reflects a transactional perspective (Sameroff & Chandler, 1975) of responsive feeding, in which infant and caregiver behaviors affect and are affected by one another over the course of feeding. Behaviors assessed for hunger and fullness in the infant and toddler were selected from a variety of sources, including the limited existing literature at the time (Crow, 1977; Gesell & Ilg, 1937; Korner, Chuck, & Dontchos, 1968; Morris et al., 1983), other measures including the Nursing Child Assessment Feeding Scale (Sumner & Spietz, 1994), qualitative research on factors influencing maternal decisions to initiate and stop feeding their infants (Hodges, Hughes, Hopkinson, & Fisher, 2008), and the clinical and research experiences of the RCFCS development team, including a nurse practitioner, a lactation physiologist, nutritionists, and a developmental psychologist.

The RCFCS includes feeding cues that reflect developmental transitions from early infancy through toddlerhood up to 2 years of age (see Table 1). There are 48 different types of feeding cues; 20 thought to reflect hunger and 28 thought to reflect fullness or satiation (Blundell et al., 2010). The RCFCS was designed to allow microanalytic coding (Bakeman & Quera, 2011) and is used to code videos of feeding interactions. Hunger cues are coded (ideally 10 minutes prior to the first bite or food to mouth in the case of breast or bottle-feeding) until the caregiver begins to prepare food (infant is placed in feeding location/position or caregiver begins to prepare food—whichever comes first). Fullness cues are coded beginning 1 minute after the 1^st bite is taken until food or the infant is removed from the feeding location. All 48 hunger and fullness cues are coded from the time of food preparation until 1 minute after the first bite in order to assess the degree of the infant’s receptiveness to or disinterest in feeding (Hodges et al., 2013). Feeding cues are categorized as early (e.g., sucking on objects, slowing or pausing), active (e.g., opening mouth wide when presented with food, pushing food away), or late (e.g., crying) to reflect the ways that infants are thought to communicate, subtly at first but increasingly overt until a response is received (Beebe & Stern, 1977).

Procedures

In the Infant Care study, mothers were video-recorded with a systematic protocol in their home environments during a feeding episode with their infants at 3, 6, 9, 12, and 18 months (Sacco, Bentley, Carby-Shields, Borja, & Goldman, 2007). The research team told mothers they and their infant would be video-recorded during feeding and a camera would be set up in the feeding location. Mothers were asked to show and tell what they were feeding their infant and to act as they normally would if the research team were not present. Once recording began, the videographer did not look directly at the mother or the infant, but instead assessed feeding progress through the camera’s viewfinder. Recording ended when the mother said feeding was completed and showed what food was remaining (if applicable). Due to the protocol with which the videos were recorded, coding of cues consistent with the RCFCS’s definition of hunger was not possible.

Two coders (authors HW and BC) received extensive training from the first author (EAH) and tested to ≥ 85% agreement against gold standard training tapes prior to coding tapes. Interrater reliability and observer drift were assessed initially through testing against a gold-standard, then every 2 months, and at the end of coding. Coding meetings were held bi-weekly. Forty tapes (~18% of the total sample) were coded by both HW and BC to assess interrater reliability through weighted Cohen’s kappa at each infant age and overall. Coders were limited to no more than 2 tapes per day and 8 tapes per week to minimize fatigue. They were blinded to the research questions and infants’ BMI Z score. Videos were randomly assigned to coders initially; then assigned a coding schedule to ensure that tapes were coded out of chronological order and no subjects had two feedings coded the same day. Weighted kappas for interrater reliability were k = 0.75 for receptiveness and k = 0.71 for fullness.

Analysis

Descriptive statistics of feeding cue frequency at each time point were used to characterize developmental progression using SPSS version 22.0

Participants

On average mothers were obese and in their early 20s at baseline (see Table 2). Less than half were currently working, >40% were not educated beyond high school, and most were single. Just over half of the infants were male. Only 20% of the infants were being breastfed at 3 months of age; 93.3% were receiving formula and 80% were already consuming solid foods, which aligns with the overall Infant Care sample (Wasser et al., 2011).

Feeding Cues

Early receptiveness cues were relatively rare over time, with sucking the most dominant, though it predictably decreased as infants transitioned to complementary foods (foods other than breastmilk or formula). Active receptiveness cues were much more common compared to early receptiveness cues, with opening mouth wide, latching on, or feeding self, predominating at each time point (see Figure 1; supplemental digital content). Rooting or nuzzling was rare in this group, seen only twice, at 3 months of age and none thereafter. However, there were patterns of increasing and decreasing of cues reflecting development over time. For example, settling into the feeding decreased from ~50% at 3 and 6 months to 4.8% by 18 months, whereas postural attention and reaching for food increased at 6 months and remained relatively stable to 18 months. Excitatory limb movements peaked at 6 months, but thereafter accounted for a relatively low percentage of active receptiveness cues overall. Fidgeting or squirming and excitatory or affirming vocalizations were infrequent. Crying, a late receptiveness cue was rarely seen, and moving the head frantically from side to side and temper tantrums were not seen at all.

Early cues indicating disinterest in feeding were most often infants taking more interest in their surroundings than food or looking away (see Figure 2; supplemental digital content). This cluster of cues jumped in frequency from 6 to 9 months and thereafter remained the most common early disinterest cue. Decreasing activity level predominated at 3 and 6 months, but decreased at 9 months and was not seen afterward. Moving the hand to the face, not opening the mouth until the spoon was at the lips, slowing or pausing, and averting the gaze were less prevalent, but persisted over time. Decreased muscle tone, turning the head in response to food, and grimacing, pouting, or frowning were rarely observed. The most prevalent active disinterest cues included detaching from the nipple and turning or pulling away abruptly (see Figure 3; supplemental digital content). These were followed in prevalence by infants: taking off their bib, attempting to leave the feeding location, refusing to open their mouths when food was presented, and playing with food or surrounding items. Other cues were more rarely seen, though infants shaking their heads or saying “No” were among the most frequent at 18 months.

In the first six months, decreasing muscle tone and activity level were the most common early fullness cues (see Figure 4). Thereafter, taking interest in surroundings was most prevalent. Slowing or pausing and bringing the hand to the face were among the most frequent early fullness cues at all time points. Overall, a transition was seen from decreasing activity to more alertness and less interest in continuing with feeding.

In the first 6 months, falling asleep and detaching from the nipple were the most frequent active fullness cues, followed by pulling or turning away abruptly (see Figure 5). Active fullness cues became increasing diverse after 6 months, led by more assertive cues such as playing with food or surrounding items, pushing or pulling away, and communicating “no” verbally or non-verbally. Detaching from nipple began its steady decrease at 12 months of age, reflecting the transition to complementary foods. Late cues, such as crying, were observed on only a few occasions (data not shown).