Abstract # 3:

Scheduled for Thursday, August 18, 2005 09:45 AM-10:00 AM: Session 1 (Parliament Room) Oral Presentation


M. Makagon1, M. J. Owren1 and E. S. Funayama2
1Cornell University, Dept.of Psychology, Cornell Univ., Ithaca, NY 14853, USA, 2Gallaudet University
     The developmental and phylogenetic origins of human laughter are not well understood, with available evidence inconsistently suggesting both innate stereotypy and high variability in laugh acoustics. We examined this issue by investigating laughter in congenitally deaf adults, using humorous video-clips to elicit laughter from 21 Gallaudet University students with little or no auditory experience, and in 24 normally hearing students enrolled at Cornell University. Acoustic analyses focused on temporal and spectral features, as well as production modes of the vocalizations. Repeated-measures ANOVA testing indicated that while deaf vocalizers produced sounds with lower amplitudes (P < 0.01) and longer durations (P < 0.01), laughter was markedly similar in the two groups. The acoustic differences likely reflect socially prescribed suppression of loud vocal displays by the profoundly deaf, but may also result from higher phonation thresholds or weakened vocal-fold responsivity in these individuals. Finding overall similarity in laugh acoustics indicates a strongly 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, which suggests a corresponding diversity, rather than stereotypy in underlying motor behavior.