International Journal of Human Diversity and Evolution
Coverage: 1923-1941 (Vols. I-XIX) & 1962-2021 (Vols. 1-59)
ISSN 0323-1119 (Print)
ISSN 2570-9127 (Online)
Special Issue dedicated to the memory of Vladimír Novotný is in preparation.

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'Zacher V, Niemitz C, 2003: Why Can a Smile Be Heard? A New Hypothesis on the Evolution of Sexual Behaviour and Voice. Anthropologie (Brno) 41, 1-2: 93-98'.
When speaking on the telephone a smiling face can be detected with some certainty by listening to the partner. For an acoustic investigation, 10 subjects were asked to read out 27 words and 4 sentences with and without a smiling face. The utterances were recorded on a Sony DAT-recorder and analysed using WinSAL 1.2a bioacoustic software. For this test, 141 adult individuals were asked to discriminate among six possible guesses of different facial expressions. The guesses of smiling voices were correct in significantly more cases than random expectation value. The subsequent analysis showed that smiling has an effect on most acoustic parameters: It raised the energetic maximum of the basal formant as well as the average frequency of the second and the third formants. The amplitude of single words increased. More than 20 other parameters tested were significantly different in smiling and non-smiling voices - included were differences in duration, in the different ways of articulation of vowels and differences between both sexes. These highly complex differences cannot merely be an effect of passive deformations of the vocal tract through smiling. Cerebral control of many unintentional parameters of communication must have a genetic basis. Human courtship behaviour is mostly done in privacy or often in poor light conditions. This may be the reason for many significant differences between the smiling and the non-smiling voice.
Smiling voice - Audible - Sex- specific - Human courtship behaviour

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