Moderate evidence for a Lombard effect in a phylogenetically basal primate

Area of Science:

• Primate vocalization
• Animal communication
• Bioacoustics

Background:

• The Lombard effect is a vocal adjustment to background noise, observed across diverse species.
• This phenomenon, crucial for auditory feedback-mediated voice control, is widespread in mammals.
• Its presence in phylogenetically basal species offers insights into evolutionary pathways.

Purpose of the Study:

• To investigate the Lombard effect in the grey mouse lemur (Microcebus murinus), a phylogenetically basal primate.
• To determine if mouse lemurs exhibit vocal amplitude adjustments in response to increased background noise.
• To explore the consistency of the Lombard effect across different contexts and individuals in this species.

Main Methods:

• Exposing grey mouse lemurs to varying levels of controlled background noise.
• Recording vocalizations to measure amplitude changes in response to noise.
• Analyzing vocal data for consistent patterns of the Lombard effect across individuals and experimental contexts.

Main Results:

• Mouse lemurs demonstrated an ability to increase vocal amplitude when exposed to enhanced background noise.
• The vocal adjustment was comparable in magnitude to that observed in other primates.
• However, the Lombard effect was not consistently observed across all individuals and contexts, indicating variability.

Conclusions:

• The Lombard effect in mouse lemurs, while present, is influenced by contextual and individual factors.
• This suggests that mammalian vocal communication, despite the general Lombard effect, involves more complex regulatory mechanisms.
• Further standardized research is needed to understand the intricacies of mammalian vocal communication and its evolutionary links to human speech.