Laughter in Congenitally Deaf versus Normally Hearing College Students: An Acoustic Analisis
The developmental and phylogenetic origins of human laughter are not well understood, with available evidence inconsistently suggesting both innate stereotypy and high variability in laughter acoustics. We examined this issue by investigating laughter in 19 congenitally deaf college students, with little or no auditory experience, and in 23 normally hearing college students. Acoustic analyses focused on temporal and spectral features, as well as vocal production modes. Repeated-measures ANOVA testing indicated marked similarity in laughter produced by the two groups. Acoustic differences that did occur in amplitudes (p < 0.01) and durations (p < 0.01) of the laughs likely reflect socially prescribed suppression of loud vocalizations by the profoundly deaf, but may also result from higher phonation thresholds or weakened vocal-fold responsivity. Finding overall similarity in laugh acoustics indicates an innate foundation for the neural circuitry involved, and that specific auditory experience is not a prerequisite for the development of these species-typical sounds. Nonetheless, laugh acoustics within both groups were also quite variable, suggesting diversity, rather than stereotypy in underlying motor behavior.
Committee members: Dr. Michael J. Owren, Dr. Michael H. Goldstein. This work was done in collaboration with Dr. Michael J. Owren and Dr. E. Sumie Funayama.
Deaf; Laughter; Laughter Acoustics; Vocal Innateness
dissertation or thesis