Push it! Encouraging Crawling Infants to act on Objects Relates to Increased Receptive Vocabulary

• In Event: The Ecology of Infant Motor Development: Diversity and Dynamics

Abstract

The onset of walking is associated with changes in caregiver verbal input and infant language development (Karasik et al., 2013; Walle & Campos, 2014). We used day-long home audio recordings (Study 1) and laboratory observations (Study 2) of same-aged crawling and walking infants to explore how caregivers’ verbal input was associated with infants’ vocabulary size.

Study 1. Day-long home audio LENA recordings of crawling (N= 23; Mage= 12.70 months) and walking (N= 25; Mage= 12.81 months) infants were collected from households with an average income of $61,000 living in a semirural area. LENA’s Automatic Data Extractor identified the 6 most voluble 5-minute samples from each infant’s recording (30 minutes total). Researchers hand coded caregiver action directives toward the infant (e.g., open it). Caregivers reported infant vocabulary using the MacArthur-Bates Communicative Development Inventory (MCDI) (Fenson et al., 1994).

Caregivers produced more action directives to walking (M= 13.29) than crawling (M= 6.38) infants, t(46) = -2.17, p = .03. A hierarchical multiple regression examined the relations of parent action directives, infant locomotor status, and their interaction with infant receptive vocabulary size. A significant Locomotor Status X Action Directives interaction was found, b = -34.71, p = .02. Specifically, crawling infants who received more action directives had larger receptive vocabularies, p = .02, but this effect was not present for walking infants (see Figure 1).

Study 2. Crawling (N= 28; Mage= 12.68 months) and walking (N= 43; Mage= 12.73 months) infants participated in a 5-minute in-lab freeplay session with their caregiver. Households had an average income of $100,000 and lived in an urban area. In-lab observations were utilized to identify how action directives related to infant-caregiver attention and object directedness, something not possible to code from the audio recordings in Study 1. Caregiver action directives were categorized into subtypes: occurring inside or outside of joint attention (JA), and then pertaining to infant object actions, attention, or physical movement. Caregivers also completed the MCDI to assess infant vocabulary.

Caregivers produced similar amounts of action directives and action directive subtypes to crawling and walking infants, ps > .12. Preliminary analyses indicated that only action directives outside JA were correlated with infant vocabulary, p = .001. Hierarchical multiple regressions examined the relations of action directives outside JA, locomotor status, and their interaction with infant receptive vocabulary. A significant Locomotor Status X Action Directives outside JA interaction emerged, b = -11.99, p = .005 (see Figure 2a). Closer examination of each subtype revealed that caregiver encouragement of infant actions on objects while not in JA predicted crawling infants’ receptive vocabularies (see Figure 2b). However, such associations were not present for other action directive subtypes nor for walking infants (see Figure 2c & 2d).

This investigation indicates that caregiver encouragement of infants’ actions was associated with crawling, but not walking, infants’ receptive vocabulary. Moreover, the similarity of results across distinct research methodologies and samples differing in socioeconomic status and geographic location adds confidence to the findings. Potential explanations and further avenues of inquiry will be discussed.

Authors

• Lukas D Lopez, University of Utah
  Presenting Author

• Eric A Walle, University of California - Merced
  Non-Presenting Author