Abstract:

Laughter is a frequently produced yet poorly understood vocal signal. Despite the lack of basic knowledge regarding this species-typical vocalization, this signal may be advantageous to study as it provides an opportunity to examine indexical cueing in the absence of linguistic content. The source-filter model of vowel production guided acoustic analysis of laughter recorded from experimentally naive subjects as they watched emotion-inducing film clips in a laboratory setting. Subjects were 48 males and 48 females tested either alone or with a same- or opposite-sex friend or stranger. Laugh acoustics were found to vary by gender, talker, and social context. Males produced predominantly unvoiced, ``grunt'' laughs, whereas female laughter was more variable and included more voiced, long duration ``song'' laughs. Discriminant function analyses revealed that source and filter-related cues were differentially associated with social context and talker identity. Variability in source-related cues, particularly F0, more successfully discriminated social context, whereas cues related to the vocal tract transfer function better discriminated among individuals. Females, but not males, had significantly higher formant frequencies when tested with opposite-sex strangers. The overall pattern of results is consistent with recent examinations of indexical cuing in human speech and nonhuman primate vocalizations. [Work supported by NIMH.]