Page 47 - Fall2019

Lawrence D. Rosenblum
Address:
Department of Psychology University of California, Riverside 900 University Drive
Riverside, California 92521 USA
Email:
lawrence.rosenblum@ucr.edu
Does Sensory Modality Matter? Not for Speech Perception
Speech perception is possible through sound, sight, and touch, and the speech brain treats all of this input the same.
Speech by Touch
Rick Joy is deaf and blind. But you wouldn’t know this from our conversation. When I ask him questions about his language training, Rick provides detailed answers on how deaf-blind individuals were taught to perceive and produce speech. He then adds “I’m probably one of the last of my kind.” He explains that he only knows of eight remain- ing individuals in the United States who have been trained to understand speech the way he understands mine: by touching my face.
Rick is using the “Tadoma” method of perceiving speech by touching my lips, jaw, and neck with the fingers of his right hand (for demonstrations of Tadoma, see bit.ly/2WQq4E7). In this way, he is able to understand me about as well as when a hearing person is conversing in a noisy restaurant. I have to repeat myself every few minutes but this doesn’t inhibit the flow of our conversation. He responds with his own speaking voice. Rick’s Tadoma skills allowed him to excel in high school and become the first blind-deaf Eagle Scout. It also allowed him to graduate college and then design circuit boards for Hewlett-Packard for 30 years.
The Tadoma technique was taught to a young Helen Keller and other deaf-blind chil- dren in the early to mid-twentieth century. These days, there are fewer deaf-blind infants (thanks to the rubella vaccine), and for those who are, cochlear implants and other technical advances have made the use of Tadoma rare. Rick Joy is one of the last individuals known to have been formerly taught the technique. I ask Rick if this makes him feel special, and he answers “Not really. Tadoma is something anyone can learn if they have the time and patience. Of course, there’s not much of that around these days.” We both laugh.
Rick is absolutely correct about Tadoma. Research shows that subjects with normal hearing and vision can learn to use the technique nearly as well as Rick does if they are willing to dedicate 100 hours to practice (Reed et al., 1985). But it is the research on Tadoma novices that is most striking. Despite most of us having little, if any, experi- ence touching faces for speech, we can all easily identify many consonants and vowels using the technique. Moreover, as soon as we touch a face for speech, we integrate the speech we feel with the speech we hear (Fowler and Dekle, 1991). For us novice users, touching the face of a talker can quickly enhance our understanding of noisy speech as well as make lipread speech easier to comprehend (Gick et al., 2008). This inher- ent utility of felt speech is evident in brain reactivity; simultaneously touching and listening to a talker speeds critical evoked responses in auditory brain areas (Treille et al., 2014). Taken together, research on Tadoma shows that despite few of us using the technique as well as Rick Joy, our brains are ready to use felt speech and use it similarly to how it uses heard speech: as information about articulation.
©2019 Acoustical Society of America. All rights reserved. volume 15, issue 3 | Fall 2019 | Acoustics Today | 47 https://doi.org/10.1121/AT.2019.15.3.47