John D. Bonvillian (1948-2018) was a psychologist and associate professor - emeritus in the Department of Psychology and the Interdepartmental Program in Linguistics at the University of Virginia in Charlottesville, Virginia. He is the principal developer of Simplified Signs, a manual sign communication system designed to be easy to form, easy to understand and easy to remember. He is also known for his research contributions to the study of sign language, child development, psycholinguistics, and language acquisition. Education, early work, and career Bonvillian received a B.A. in Psychology from Johns Hopkins University in 1970. While an undergraduate there, he was introduced to the field of child development by Mary D. S. Ainsworth and to psycholinguistics by James E. Deese. He then attended Stanford University on a National Science Foundation doctoral fellowship, earning his Ph.D. in 1974. As a graduate student, he worked primarily with Keith E. Nelson as they conducted studies on child language acquisition in typically developing children and children with disabilities. Some of this work was later reprinted in other publications. He also wrote several articles examining the impact of maternal language input and other behaviors on a child's subsequent development. During his time at Stanford, John met William C. Stokoe, a pioneering figure in sign language research. Subsequently, the two were to work together editing the journal, Sign Language Studies. In 1974, Bonvillian accepted an appointment as an assistant professor at Vassar College. In 1978, he was invited to join the faculty at the University of Virginia, where he was reunited as a colleague with his former professors, Ainsworth and Deese, who had previously accepted appointments at Virginia. He taught at UVA until his retirement in May 2015. He died on May 8, 2018, at the age of 69. Research Sign language acquisition and development In 1979, Bonvillian commenced the first of two longitudinal studies of sign language acquisition in young children with deaf parents. These studies (conducted primarily with Michael D. Orlansky and Raymond J. Folven) were to provide valuable information on the course of American Sign Language (ASL) acquisition. Their research found that the patterns with which children developed proficiency in ASL was highly similar to the patterns with which children acquired spoken language skills. While the pattern of acquisition was similar across language modalities, many of the sign-learning children attained different language milestones in ASL earlier than their hearing counterparts attained these same milestones