The Motor-Vocal Interplay: Understanding how Motor Activity relates with Early Speech Development

Motor development and language development have historically been considered separately and viewed as independent domains from different theoretical perspectives. In recent decades however, motor theory of speech perception and the embodied cognition approach have prompted many researchers to study the co-development of motor and linguistic abilities. The present study investigates whether the variation in the daily motor activity in infants with different motoric competences (i.e., crawlers vs non-crawlers) is somewhat linked with the amount of infant vocalizations. To investigate this, data were collected from a sample of 26 infants in the babbling phase between 8 and 12 months. The study employed actigraphy technology (Motionwatch 8, CamNtech) to quantify motor activity across day, and LENA technology (Language Environment Analysis) to quantify infant’s vocal production. The main finding, focusing on periods in which infants were free to move and explore actively (e.g., during free play), showed a significant positive correlation emerged between daily movement and vocalization, only in the crawling group. These results suggest that language development and active motor behavior are interconnected: the amount of motor activity may partially predict the amount of vocal activity, indicating that the two systems could reflect a shared underlying developmental mechanism. This relationship may also depend on the specific motor milestone reached by the infant at a given stage. In particular, while the effort involved in learning to crawl may initially reduce babbling, mastery of this skill may subsequently promote vocalization by granting infants greater independence and opportunities for exploration.