Humans need auditory experience to produce typical volitional nonverbal vocalizations

Area of Science:

• Evolutionary biology
• Neuroscience
• Linguistics

Background:

• Human nonverbal vocalizations like screams and cries have evolved functions.
• While some vocal signals are reflexive, many emotional vocalizations are voluntary.
• Voluntary vocalizations may require auditory input for typical development, analogous to speech.

Purpose of the Study:

• To investigate the acoustic properties of volitional vocalizations in profoundly deaf adults.
• To compare vocalizations from deaf individuals with those from typically-hearing controls.
• To assess the impact of auditory deprivation on the production and perception of emotional vocalizations.

Main Methods:

• Acoustic analysis of hundreds of volitional vocalizations from deaf adults and hearing controls.
• Perception experiments involving 444 participants assessing emotion identification, authenticity, and deafness detection.
• Comparison of vocalizations based on auditory experience, including congenitally deaf individuals.

Main Results:

• Deaf adults produced higher-pitched, less articulated, and less varied aggression and pain vocalizations.
• Fear vocalizations from deaf adults were acoustically more typical than other emotional vocalizations.
• Listeners were less accurate in identifying emotions, perceived vocalizations as less authentic, and detected deafness more readily in deaf individuals' vocalizations.
• Congenitally deaf individuals exhibited the most atypical vocalizations, indicating additive effects of auditory deprivation.

Conclusions:

• Auditory input is essential for the typical development of volitional non-linguistic vocalizations, not just speech.
• Vocal learning plays a critical role in acquiring the full range of human emotional vocal expression.
• Auditory deprivation significantly impacts the production and perception of emotional vocalizations.