Good rhythm production by deaf children with cochlear implants

Takayuki Nakata1, Sandra E. Trehub2, Chisato Mitani1, Yukihiko Kanda3, Hidetaka Kumagami3, Kenji Takasaki3 & Haruo Takahashi3

1Nagasaki Junshin Catholic University, Japan 2University of Toronto at Mississauga, Canada 3Nagasaki University, Japan

The cochlear implant is an auditory prosthesis designed to enable users to perceive and produce speech sounds. The prosthesis provides good temporal information, which facilitates the processing of speech sounds, but degraded spectral information, which impairs music processing. In general, implanted adults, who are usually postlingually deaf, show little interest in music, even if they were music lovers prior to their hearing loss. We found, however, that congenitally deaf children with cochlear implants are keenly interested in music, even though they seem unable to perceive melody. On the basis of parental reports of children's spontaneous singing at home (13 of 15 parent questionnaires), we sought to examine implanted children's singing under controlled conditions. Accordingly, we recorded informal performances of the favorite songs of six congenitally deaf children with cochlear implants, who were 5-10 years of age, and one normally hearing child, who was 5 years of age. Acoustical analyses of the songs revealed relative timing skills by all implanted children (average of absolute percent deviation from target interval durations or DTD = 14.91%, 20.96%, 12.79%, 7.32%, 24.34%, 36.10%, 33.01%) that were similar to the relative timing skills of the single hearing child (DTD= 33.01%). Remarkably, the pitch interval deviations of two implanted children [average of absolute deviation in cents (100 cents = 1 semitone) or DPI = 186.78 and 171.74 cents] were comparable to those of the hearing child (DPI= 167.16 cents), but four other implanted children had much larger pitch interval deviations (DPI= 319.96, 246.40, 242.92, and 244.90 cents). Note, however, that these large pitch deviations are considerably smaller than the estimated pitch resolution thresholds of implanted adults. It would appear that good rhythmic perception, even in the absence of melody perception, makes music accessible and enjoyable for those who have never experienced music otherwise. It is also possible that the plasticity of the young brain facilitates perceptual learning in the domain of music, as in other domains.