Professor Nathan Fox
My graduate student, Efrat Schorr proposed a study of children who received cochlear implants. She was interested in the effects of early experience on their speech perception and emotional development. She received funding from NIH and from the American Hearing Foundation for the research. As a result of input from me and Dr. Eric Knudsen at Stanford, she included a task designed to assess speech perception in these children. The task was provided by David Poeppel , who is in the Biology department here at Maryland, and his post doctoral fellow, Virginie Van Wassenhove, who worked with Efrat in setting up the experiment.
2) Where were the children tested?
The study took place in the Child Development Laboratory, which is housed in the Department of Human Development/Institute for Child Study here at the University of Maryland.
3) You say that speech is "bimodal" - what does that mean?
The signals that hearing people receive that contain information about speech are both auditory and visual. They hear people talking and they see their faces, hence their lips moving. When what they hear and the lips moving (what they see) are congruent, we say that is bimodal congruent speech stimuli.
4) Why is this different for a deaf person?
A deaf person can only see a person's face and lips moving. They cannot hear the sounds. Thus they have to rely on lip-reading or American Sign Language (using hand motions) to "converse."
5) The deaf children tested over an 18-month period were between four and 14, and had had their cochlear implants for at least a year. Did the study find that early intervention was important in their auditory development?
We found that when the speech stimuli were congruent - that is, both auditory and visual stimuli were synchronized together - the children with cochlear implants did as well as normal-hearing children. When the speech stimuli were not congruent (when the lips said one thing and the voice said another) then children with cochlear implants did not do as well as hearing children. One key factor in determining how good a child with cochlear implants was at this task was when he or she got the implant. The earlier they got the implant, the better they did on perceiving the incongruent speech stimuli.
6) What is interesting about this study is that is shows children who wait to get cochlear implants after two-and-a-half years of age have greater problems "fusing" both visual and speech perception.
That's right. Children who received the cochlear implant after two-and-a-half didn't do as well as children who received the implant earlier. The ability to "fuse" auditory and visual information in the speech stream is something that we take for granted, something that develops early in life. If you lack in its development then your ability to perceive the totality of the speech stream is impaired.
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