The Effects of Deafness and Visual Language Experience on Visual Perception from Infancy to Adulthood

University Of California-San Diego, La Jolla CA

Investigators

Abstract

Deaf individuals must rely more than hearing individuals on visual information to understand what is happening in the world around them. As a result, the brains of deaf people typically reorganize to help them make better use of the available visual information. The questions addressed by this research project are whether and how greater reliance on visual information actually changes visual experiences. The project also investigates how differences between hearing and deaf people's visual processing develop across infancy, childhood, and adulthood. There is evidence that aspects of vision are altered or enhanced in deaf people, providing evidence for plasticity of the human brain to compensate for the absence of sound. Yet, very little is known about how these alterations emerge during development. This project investigates the consequences of altered early sensory experience during development, measuring perceptual sensitivity to motion, form, faces, and objects. Deaf people may have altered processing of these aspects of vision for two reasons. First, lack of auditory input compels deaf people to rely more on their intact visual modality, and, second, many deaf people use a visual language (American Sign Language, ASL), which may enhance certain aspects of visual processing that convey critical linguistic information. To tease apart effects of deafness versus ASL language experience, the studies will compare visual sensitivity in Deaf and Hearing individuals who are either Signers or Nonsigners. Also, effects of deafness could occur during an early critical period rather than due to accumulated altered sensory experiences across the lifespan. To address this possibility, the project will also involve studying a group of "Hearing Restored" children who received cochlear implants around 12-18 months, following a period of auditory deprivation starting at birth. Results from these studies will reveal how sensory systems adjust to altered input and elucidate mechanisms of brain plasticity, which may have widespread implications for deaf and blind individuals, as well as for those who lose their hearing or sight later in life.