Ensemble perception, categorization, and high-level visual search

Abstract

Introduction. 1- Categorization is a fundamental sensory-motor ability facilitating rapid behavioral responses to complex situations. It is recognition of shared features or similarities between objects, events, or ideas, and their organization into associated abstract groups. Categorization allows responding similarly to category members: chairs are for sitting; food for eating; friends for approaching; foes for avoiding. 2- High-level visual search tests categorization, since it is based on requesting observers to find exemplars of named categories among heterogeneous objects. 3- Ensemble perception is the ability to efficiently represent groups of similar objects by their summary statistics. Studies found that observers are better at perceiving the mean of a set of images than remembering the presence of a particular member of the set. Observers also automatically and implicitly extract averages of sets of images, on-the-fly, on a trial-by-trial basis. Note that there is an inherent paradox in both categorization and ensemble perception: category exemplars and ensemble images share sufficient features to allow recognizing them as category or set members, but each one is different, or we would have a useless tautology. Methods. We now use the “individual differences” paradigm, asking if categorization, high-level visual search, and ensemble perception depend on the same or different underlying mechanisms. If separate mechanisms exist, then Nature’s manipulations (including in neurotypically-developed participants and those on the autism spectrum) may lead some individuals to have particularly sensitive mechanisms for one, and other individuals for the other. Crucially, performance subserved by different mechanisms should predict each other less than performance subserved by the same mechanism. Results. We find correlated performance for face detection and basic-level ensemble perception, but uncorrelated performance for complex categorization and ensemble perception or face detection. Conclusions. These results have important implications for placing these perceptual mechanisms at low-levels versus high-levels of the visual hierarchy.