<p>Relationships between motor development and language abilities have been consistently reported in previous literature. One of the relationships that has becoming increasing popular is the link between walking and language. Whereas research has demonstrated that onset of walking is related to communicative skills and vocabulary abilities (e.g., Clearfield, 2011; Walle & Campos, 2014), the mechanism underlying this relationship remains unclear. One potential explanation is that walking increases young children’s opportunities to interact with objects and explore the environment. Young children’s ability to adapt gait while playing is necessary for successful navigation of their environment and may be one factor underlying the walking-language relationship. However, little research has examined how young children adapt gait when interacting with objects in their environment when they are free to walk in a naturalistic manner. Additionally, how young children’s gait control and behavior during free-play is related to word learning has also been understudied. The purpose of this dissertation was to quantify how new and experienced walkers adapt gait behavior based on task (carrying objects compared to not carrying objects) and environmental constraints (free-play versus straight-path) and assess how these behaviors may be related to language abilities early in development. </p> <p><br></p><p>Chapter 3 examined how object carriage impacts gait characteristics and behavioral measures of stability during free-play and a straight-path task. New (13-month-olds) and experienced (24-month-olds) walkers engaged in a 20-minute free-play session with their parents. Eighteen toys that varied in size and weight were provided. Following the free-play session, new and experienced walkers engaged in a straight-path task where they were encouraged to walk from their parents to the experimenter, take a toy, and carry the toy back to their parent. Overall, size and weight did not appear to impact lower-body gait characteristics. Although there were no differences in lower-body gait control when carrying a toy compared to not carrying a toy, there were individual differences in how young children adapted their step length, step width, and stride speed with some children adopting more mature gait characteristics and others adopting less mature gait patterns. Young children’s lower-body gait also differed based on environmental constraints (free-play versus straight-path task). In addition to these lower-body findings, new and experienced walkers also adapted their upper-body control when carrying toys in both free-play and the straight-path task. New walkers also appear to focus on weight of the toy when selecting toys to carry whereas experienced walkers did not demonstrate preference for specific toy characteristics. </p> <p><br></p><p>Chapter 4 assessed the relationship between gait characteristics and functional behavior during free-play and communicative/vocabulary abilities in new and experienced walkers. Thirty-eight new walkers and thirty-eight experienced walkers from Chapter 3 were included in the analyses. Additionally, thirteen new walkers also returned at 24-months and repeated the data collection procedure for a longitudinal analysis of these relationships. The protocol for Chapter 3 was the same as Chapter 4; however, only free-play measures were included in the analyses. Parents also filled out the age-appropriate version of the MacArthur-Bates Communicative Development Inventory as a measure of communicative/vocabulary abilities. Overall, the results of Chapter 4 demonstrated that quality of upper-body gait control and time spent in motion were significant predictors of new walkers’ communicative skills and vocabulary abilities. Whereas these relationships were not apparent in the experienced walking group, quality of gait at 13-months was predictive of productive vocabulary scores at 24-months of age. </p> <p><br></p><p>Taken together, the results from these studies suggest that examining gait behavior during free-play reveals how complex young children’s navigation of their environment is. Furthermore, these early movements and functional behavior during free-play may be important predictors underlying the relationship between onset of walking and language development.</p>