Innate face-selectivity in the brain of young domestic chicks

Shortly after birth, both naïve animals and newborn babies exhibit a spontaneous attraction to faces and face-like stimuli. While neurons selectively responding to faces have been found in the inferotemporal cortex of adult primates, face-selective domains in the brains of young monkeys seem to develop only later in life after exposure to faces. This has fueled a debate on the role of experience in the development of face-detector mechanisms, since face preferences are well documented in naïve animals, such as domestic chicks reared without exposure to faces. Here, we demonstrate that neurons in a higher-order processing brain area of one-week-old face-naïve domestic chicks selectively respond to a face-like configuration. Our single-cell recordings show that these neurons do not respond to alternative configurations or isolated facial features. Moreover, the population activity of face-selective neurons accurately encoded the face-like stimulus as a unique category. Thus, our findings show that face selectivity is present in the brains of very young animals without preexisting experience.