Reach on sound: a key to object permanence in visually impaired children.

BACKGROUND: The capacity to reach an object presented through sound clue indicates, in the blind child, the acquisition of object permanence and gives information over his/her cognitive development. AIM: To assess cognitive development in congenitally blind children with or without multiple disabilities. STUDY DESIGN: Cohort study. SUBJECTS: Thirty-seven congenitally blind subjects (17 with associated multiple disabilities, 20 mainly blind) were enrolled. OUTCOME MEASURES: We used Bigelow's protocol to evaluate "reach on sound" capacity over time (at 6, 12, 18, 24, and 36 months), and a battery of clinical, neurophysiological and cognitive instruments to assess clinical features. RESULTS: Tasks n.1 to 5 were acquired by most of the mainly blind children by 12 months of age. Task 6 coincided with a drop in performance, and the acquisition of the subsequent tasks showed a less agehomogeneous pattern. In blind children with multiple disabilities, task acquisition rates were lower, with the curves dipping in relation to the more complex tasks. CONCLUSIONS: The mainly blind subjects managed to overcome Fraiberg's "conceptual problem"--i.e., they acquired the ability to attribute an external object with identity and substance even when it manifested its presence through sound only--and thus developed the ability to reach an object presented through sound. Instead, most of the blind children with multiple disabilities presented poor performances on the "reach on sound" protocol and were unable, before 36 months of age, to develop the strategies needed to resolve Fraiberg's "conceptual problem"