The perceptual categorization of multidimensional stimuli is hierarchically organized

Abstract

As we interact with our surroundings, we encounter the same or similar objects from different perspectives and are compelled to generalize. For example, we recognize dog barks as a distinct class of sound, despite the variety of individual barks. While we have some understanding of how generalization is done along a single stimulus dimension, such as frequency or color, natural stimuli are identifiable by a combination of dimensions. To understand perception, measuring the interaction across stimulus dimensions is essential. For example, when identifying a sound, does our brain focus on a specific dimension or a combination, such as its frequency and duration? Furthermore, does the relative relevance of each dimension reflect its contribution to the natural sensory environment? Using a 2- dimension discrimination task for mice we tested untrained generalization across several pairs of auditory dimensions in a naturalistic and automatized behavioral paradigm. We uncovered a perceptual hierarchy over the tested dimensions that was dominated by the sounds spectral composition. This hierarchy could reflect the relevance of the different dimensions in natural stimuli and their potentially associated differential shaping of neuronal tuning. Mice could learn to pay more attention to dimensions low in the hierarchy, but this learning was more rigid and did not generalize as flexibly. Stimuli are thus not perceived as a whole but as a combination of their features, each of which weights differently on the dentification of the stimulus according to an established hierarchy.