Deaf Blind Project
Differences between sign language and spoken language may reflect differences in language modality, differences in linguistic properties or both. We have undertaken three studies of signers with Usher syndrome to explore how loss of vision can affect the production and perception of sign language.
Calibration of signing space: the role of visual feedback
2. Utilising signing space: the role of visual imagery
3. How does the brain process tactile language?
1. Signing space
The first study compared signing space in normally sighted individuals and those with Usher Syndrome who have ‘tunnel vision’, asking what influences the size of signing space. We found that the hands are not kept within the visual field, but move in and out of the periphery of the visual field. This suggests that the size of signing space is calibrated by using the limits of the visual field to decide how large the space should be.
2. Hands-on Signing: Spatial Description Study
This study aimed to explore the role of vision in perceiving and producing BSL by looking at face and body information, the use of classifiers, and pointing. We compared normally sighted signers wearing blindfolds with deaf-blind signers and found that deaf-blind signers used less facial expression in their signing. They also used fewer classifiers but more pointing when describing arrangements of toys. These differences suggest that people who have lost their vision permanently may be less efficient at generating a visual representation (requiring classifiers) than those who are just temporarily blindfolded.
3. How does the brain process tactile language? Since sign languages can be perceived tactilely as well as visually, we can examine the how the brain processes language using the same linguistic material conveyed in two different modalities: visually and manually. This study involved fMRI scanning of normally sighted signers and signers with Usher syndrome who still had some central vision. They received fingerspelling either visually, or through the deaf-blind manual alphabet
We found the same areas of brain activation for fingerspelling whether it was perceived visually or manually. In people with Usher syndrome, we found activation in classical language regions for both types of fingerspelling. However, there are differences in other areas of the brain – visual and sensori-motor areas, showing that the modality in which language is received affects how the brain processes language.