title: A texture-processing model of the 'visual sense of number'.
abstract: It has been suggested that numerosity is an elementary quality of perception, similar to colour. If so (and despite considerable investigation), its mechanism remains unknown. Here, we show that observers require on average a massive difference of approximately 40% to detect a change in the number of objects that vary irrelevantly in blur, contrast and spatial separation, and that some naive observers require even more than this. We suggest that relative numerosity is a type of texture discrimination and that a simple model computing the contrast energy at fine spatial scales in the image can perform at least as well as human observers. Like some human observers, this mechanism finds it harder to discriminate relative numerosity in two patterns with different degrees of blur, but it still outpaces the human. We propose energy discrimination as a benchmark model against which more complex models and new data can be tested.
authors.affiliation: Max Planck Institute for Neurological Research, PO Box 41 06 29, Cologne 50866, Germany m.morgan@nf.mpg.de.
authors.forename: M J
authors.initials: MJ
authors.lastname: Morgan
authors.affiliation: Max Planck Institute for Neurological Research, PO Box 41 06 29, Cologne 50866, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Raphael
authors.affiliation: Institute of Ophthalmology, University College London, Bath St., London EC1V 9EL, UK.
authors.forename: M S
authors.initials: MS
authors.lastname: Tibber
authors.affiliation: Institute of Ophthalmology, University College London, Bath St., London EC1V 9EL, UK.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Dakin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003198:Computer Simulation; D015350:Contrast Sensitivity / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology*
keywords: numerosity; psychophysics; texture perception