Researchers at the University of Geneva have found that specific regions of the human auditory cortex respond particularly strongly to chimpanzee vocalizations compared with those of other primates, including bonobos and macaques. The work, published as a reviewed preprint in eLife, suggests that human brain areas involved in voice processing are also tuned to certain nonhuman primate calls, reflecting shared evolutionary and acoustic roots.
The study, led by scientists from the University of Geneva’s Faculty of Psychology and Educational Sciences, examined whether human brain regions that specialize in processing voices also respond to the calls of other primates.
Using functional magnetic resonance imaging (fMRI), the researchers recorded brain activity in 23 adult participants while they listened to vocalizations from four primate species: humans, chimpanzees, bonobos and rhesus macaques. During the experiment, participants were exposed to these calls while the team modeled and statistically controlled for key acoustic features of the sounds.
According to the University of Geneva release and the reviewed preprint in eLife, the analysis revealed that a part of the auditory cortex known as the temporal voice areas, located along the superior temporal gyrus, showed enhanced activity for chimpanzee calls. In bilateral anterior sections of the superior temporal gyrus, activation for chimpanzee vocalizations was stronger than for calls from the other species, including human voices, even after accounting for basic acoustic parameters.
This pattern was particularly notable when chimpanzee calls were compared to bonobo calls. Although bonobos are as closely related to humans as chimpanzees in evolutionary terms, their vocalizations differ more in their acoustic structure. The authors report that the human temporal voice areas were especially sensitive to chimpanzee calls, which are both phylogenetically and acoustically closer to the human voice than bonobo calls.
“We wanted to know whether a subregion specifically sensitive to primate vocalizations exists,” said Leonardo Ceravolo, a research associate at the University of Geneva and first author of the study, in statements released by the university. “When participants heard chimpanzee vocalizations, this response was clearly distinct from that triggered by bonobos or macaques.”
The team also observed activity within the temporal voice areas for macaque vocalizations, though the most pronounced, species-specific effect in anterior superior temporal regions was linked to chimpanzee calls. Overall, the findings indicate that both evolutionary relatedness and detailed sound structure contribute to how the human brain processes nonhuman primate vocalizations.
“We already knew that certain areas of the animal brain react specifically to the voices of their fellow creatures. Here, we show that a region of the adult human brain, the anterior superior temporal gyrus, is also sensitive to non-human vocalizations,” Ceravolo noted, as quoted in the University of Geneva and ScienceDaily summaries of the work.
The authors suggest that these results support the idea of an evolutionary continuity in vocal processing between humans and great apes. The sensitivity of human temporal voice areas to chimpanzee calls, they argue, may reflect neural mechanisms that predate the emergence of articulated human language.
Researchers say this line of work could help clarify how the neural basis of voice recognition develops over the lifespan. University of Geneva communications materials note that such findings may eventually inform theories about how infants begin to recognize familiar voices, possibly even before birth, although this specific developmental question was not directly tested in the current study.
