Human infant cries communicate distress and elicit sex stereotypes: Cross cultural evidence

The degree to which culture and context contribute to variability in human behaviour is a critical scientific question. While most research in the human behavioural sciences is based on WEIRD samples, the last decade has seen a rise in research on traditionally under-represented populations, including small-scall societies, to demonstrate reproducibility of results. Considering this framework as a major objective, here we explore cross-cultural ubiquity in the production and perception of human baby cries, focusing on remote rural communities in the Democratic Republic of Congo, compared to analogous data from French and British samples. Through acoustic analysis of Congolese baby cries recorded in natural discomfort (bath) and pain (vaccine) contexts, combined with psychoacoustic experiments on Congolese adult listeners, we show that distress is reliably encoded in the acoustic cry signal, namely in nonlinear acoustic phenomena. Despite the absence of sexual dimorphism in cries, low-pitched cries are more often perceived as produced by boys than girls, and cries experimentally attributed to boys are perceived as expressing more distress than the same cries experimentally attributed to girls. Having obtained similar results in European samples, this study provides compelling evidence that these voice-based stereotypes are stable and robust, observed across extremely distinct human populations.