Cochlear Implants: For Many an End to Silence

Many formerly deaf people can now hear, in part, because of psychology.

Findings

In the early 1860s, Hermann von Helmholtz, one of the founders of psychology, briefly devoted himself to understanding the perception of sound and music. Like many other scientists who studied hearing in the 19th century, Helmholtz believed that we perceive sounds of different pitches based on "resonance." In other words, Helmholtz thought that some noises sound higher than others because of differences in the frequency of the sound waves responsible for the noises. However, von Helmholtz went further than his predecessors by theorizing about the precise physiological basis of hearing (e.g., he argued that receptors in different physical locations on the basilar membrane - a coiled structure imbedded in the inner ear - respond to sound waves of different frequencies). Experiments conducted by the Nobel-prize winning physicist Georg von Bèkèsy later confirmed and refined many of von Helmholtz's ideas. Almost 100 years later (in the late 1950s), another important psychologist, the renowned psychophysicist S. S. Stevens, helped refined Helmholtz's ideas further. Stevens and others showed that our auditory system organizes sounds into 24 distinct channels. Their work allowed physiologists to begin to describe the biological basis of hearing at a very precise level - a level so precise that researchers began thinking seriously about whether they could create a "bionic ear."

After a great deal of additional research, pioneering scientists in the 1960s gave a few brave deaf patients cochlear implants (small electrical devices surgically implanted in the inner ear) that provided the users with a very limited ability to detect simple properties of sound (e.g., to distinguish speech from non-speech, to determine how many syllables were in a word). Finally, in the 1970s, several independent research groups in the U.S. and Australia began the serious work of developing and testing multi-electrode cochlear implants. In 1991, Blake Wilson discovered a way to greatly increase the precision and clarity of cochlear implants (by sending electrical signals sequentially rather than simultaneously). By 1998, more than 18,000 people with no or little hearing had received cochlear implants.

Significance

It is important to note that dozens of researchers in areas of science ranging from physics and engineering to physiology, computer science, and telecommunications have all played important roles in the development of cochlear implants. Because of the magnitude of the problem of deafness, basic and applied research teams all over the world (e.g., the House Ear Clinic in Los Angeles, the Bionic Ear Institute in Australia) have worked tirelessly to develop and refine cochlear implants. However, it is clear that without von Helmholtz's groundbreaking work on the physiology and psychology of hearing, none of the work that followed it would have been possible.

Practical Application

In 2004, an issue of Hearing Health reported that, worldwide, 59,000 people have received cochlear implants and that 23,000 of these recipients live in the U.S. They also report that nearly half of all recipients of cochlear implants are children. Today many formerly deaf people can hear, in part, because of von Helmholtz's early efforts to understand the physics, physiology, and psychology of hearing. The technology is now sufficiently refined that many previously deaf users with cochlear implants can carry on a normal conversation. For adult patients who became deaf after having had normal hearing, or for children who receive cochlear implants before the age of two, cochlear implants typically produce hearing that enables normal communication, even over the telephone. As cochlear implants continue to improve, their output will likely more closely simulate that of the healthy human ear.


 American Psychological Association, February 19, 2004