Mainstream early childhood education programs promote learning through active tactile exploratory behaviors, believing that object exploration provides opportunities for multisensory integration of motor activity, cognitive processing, and social interaction, all of which are important for optimal cognitive and language development. Yet how deaf signing children explore objects, and how their tactile exploratory behaviors impact their language development has not been evaluated. Deaf signing children may explore their surroundings in the classroom in adaptive ways that afford learning benefits for them. In this proposal, we describe and classify tactile exploratory and communicative behaviors of deaf preschoolers during free play activities in an ASL-primary classroom. We will assess this using a multiple-camera system installed in the classroom and with lightweight, miniaturized inertial measurement (IMU) bilateral wristbands that each contain an accelerator, gyroscope, and magnetometer. From combined video-IMU data, several exploratory (reaching, touching, manipulating) and communicative (signing, gesturing, attention-getting) behaviors will be coded with trained human coders and machine learning body action classification algorithms. Data will be collected over three years per child, between ages 2 to 6 years. Cross-lagged panel modeling will uncover the causal directionality of effects between the frequency and duration of tactile exploratory and communicative behaviors over time. One year later, we assess word production fluency. We apply multiple regression modeling to test the hypothesis that that children who were more “hands on” explorers between ages 2-6 years will have higher word production at later ages 6-8 years. The unique, rich environment, where teachers are deaf, fluent in ASL, and the child is placed at the center of accessible, active learning, has much to inform educational practices of all children and much to reveal about how ubiquitous and unique sensory and language experiences shape cognitive development. The JSMF opportunity-award for Understanding Human Cognition is well-suited for studying continuity and change of exploratory behaviors in a naturalistic, yet consistent, environment with systematic observation. From a public health perspective, addressing significant gaps in language and literacy development for young deaf children is a critical issue for educators. Broadly, understanding alternative paths to learning in children who grow up with a signed rather than spoken language can provide refinement of theoretical perspectives about cognitive development. Future studies will assess whether exploratory behaviors are similar or different for deaf and hearing signing/nonsigning children. Resulting methods and de-identified data will be shared openly.