Evolutionary continuities and discontinuities in affective voice signaling

Area of Science:

• Evolutionary biology
• Comparative psychology
• Bioacoustics
• Human communication

Background:

• Affective voice signaling is crucial for social interactions across species.
• Voice communication evolves diverse affective signals, from basic bursts to human prosody.
• Affective prosody, unique to humans, is hypothesized as the most evolved and distinct signal type.

Purpose of the Study:

• To compare acoustic distinctiveness and perceptual decoding of nonverbal affect signals and affective prosody in humans.
• To investigate the evolutionary continuity between species-shared nonverbal affect signals and human-exclusive affective prosody.

Main Methods:

• Comparative analysis of acoustic features in nonverbal affect signals and affective prosody.
• Perceptual decoding experiments to assess the recognizability of basic affect categories from both signal types.
• Focus on human vocalizations, comparing signals with different evolutionary backgrounds.

Main Results:

• Basic affect categories are encoded in both signal types, but with minimal acoustic code continuity.
• Decoding affective meaning from affective prosody is significantly impaired, especially for positive affects and disgust.
• Recognizability of threat signals is preserved in affective prosody, unlike other affect categories.

Conclusions:

• Significant discontinuities exist between nonverbal and paraverbal (prosodic) affect signals in human voice.
• Speech acoustics may constrain affect encoding in human prosody, leading to decoding impairments.
• The findings question the direct evolutionary precursors of human affective prosody in nonverbal affect signaling.