Visual field asymmetries for motion processing in deaf and hearing signers

Area of Science:

• Neuroscience
• Cognitive Science
• Linguistics

Background:

• Previous research indicated a right visual field advantage for motion processing in deaf signers, potentially linked to auditory deprivation or American Sign Language (ASL) use.
• Hearing nonsigners showed a slight reverse asymmetry, highlighting the need to differentiate between these factors.

Purpose of the Study:

• To investigate whether the visual field asymmetry observed in deaf signers is due to auditory deprivation or ASL experience.
• To compare visual field processing (left/right, superior/inferior, peripheral/central) across deaf signers, hearing native signers, and hearing nonsigners.

Main Methods:

• Subjects performed a direction-of-motion discrimination task across various visual field locations.
• Three groups were tested: deaf signers, hearing native signers (hearing parents, ASL users), and hearing nonsigners.

Main Results:

• A robust right visual field advantage for motion processing was confirmed in deaf signers and also observed in hearing signers, suggesting an ASL-related effect.
• Deaf subjects showed a significantly larger inferior visual field advantage compared to hearing groups.
• Deaf subjects trended towards better peripheral visual processing, unlike hearing groups who favored central stimuli.

Conclusions:

• Experience with sign language, specifically ASL, recruits the left hemisphere for motion processing, leading to a right visual field advantage.
• Auditory deprivation in deaf individuals contributes to distinct advantages in inferior and peripheral visual field processing.
• Visual field asymmetries appear to be sensory in origin, not modulated by attentional factors.