A new study published in the Journal of Neuroscience has revealed that our closest relatives, the chimpanzees, also employ right-hemispheric over left-hemispheric neural correlate to process faces.
For humans, faces are one of the most critical social stimuli, carrying important information such as identity, attentional and emotional states, etc. Because of this, we humans have specific brain areas responsible for face processing and it is also widely acknowledged that our internal face processing machinery is governed more by right-hemispheric than left-hemispheric neural correlate. Even though reports are accumulating that other primate species also process faces in a similar manner, employing face-specific areas in the brain similar to those of humans, it is an open question whether and to what extent a right-hemisphere preference of processing faces exists across primate brains. This new study, led by JSPS Postdoctoral Fellow Dr. Christoph Dahl and CICASP’s own Dr. Ikuma Adachi, investigated chimpanzees’ ability to discriminate chimeric faces of both other chimpanzees and humans, i.e. the combination of either the left or right sides of faces were vertically flipped and merged into a complete face. They found an effect of choosing the left-chimeric face more often than the right-chimeric face as being the one of the two that is closer to the original face, reflecting an advantage for the right side of the brain to process faces, as reported in humans. Furthermore, they found a modulation by age of the participants, suggesting that the exposure history with a particular category shapes the right-hemispheric neural correlate to a configural/holistic processing strategy.