A Visual Behavioral Training Study of Categorical Face Pattern Recognition in Mice.

Can rodents form a categorical face concept or is their ability to discriminate faces from objects driven solely by visual features? To answer this question, we trained C57BL/6J mice on a touchscreen face-object discrimination task and examined their behavior in two experiments. We show that: (i) after training, mice generalized face-object classification to novel exemplars but lost the ability to discriminate when stimuli were inverted or contrast‑negated, consistent with the classic effects of these manipulations on humans performing categorically face-specific tasks; (ii) along a continuum from low‑similarity pareidolia to real faces, choice performance followed a sigmoidal rather than a linear or quadratic function, which again suggests a categorical face concept recognition boundary. These behavioral results in mice resemble how humans visually categorize faces and nonfaces. The work provides evidence that a face concept can emerge even in a species whose social communication is not primarily visual, paving the way for future investigations on neural and genetic substrates of categorical pattern recognition.