Nonverbal intelligence and verbal achievement in deaf adolescents: an examination of heredity and environment.

Abstract

The present study assessed the differences in intelligence and achievement of deaf adolescents from three family constellations: (a) 19 deaf children with deaf parents (dc/dp), (b) 19 controls with hearing parents and hearing siblings matched to the dc/dp group (dc/hp 1), (c) 20 deaf children with deaf siblings and hearing parents (dc/ds), and (d) 20 deaf controls with hearing parents and hearing siblings matched to the dc/ds group (dc/hp 2). Subjects were matched on 16 variables to control for extraneous factors. Dependent variables included nonverbal intelligence, vocabulary achievement, reading comprehension, language achievement, and sign language experience. The results indicated that the relationships of nonverbal intelligence, verbal achievement, and early sign language are more complex than was apparent in past studies.