This chapter focuses on the infant's motivation to explore the inanimate environment, with relatively little attention paid to social motivation or socially mediated expressions of motivated behaviour. It describes the development of mastery motivation in a sample of normally developing deaf infants from hearing families, and to examine the responses to a lack of auditory contact with the environment. The data contained in the report were obtained as part of a longitudinal investigation of the early development of deaf infants born to hearing families. The chapter describes the social, motivational and language development of deaf infants, and involved a series of observations in a laboratory setting when they were 9, 12 and 18 months old. In addition to recruitment efforts at the Gallaudet University, four experienced research groups: University of Texas-Dallas, University of Pittsburgh, Georgia State University-Atlanta, and University of Massachusetts-Amherst agreed to collaborate in the recruitment and videotaping of the deaf infants.