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A common visual metric for approximate number and density.

Dakin, SC; Tibber, MS; Greenwood, JA; Kingdom, FA; Morgan, MJ; (2011) A common visual metric for approximate number and density. Proceedings of the National Academy of Sciences of the United States of America , 108 (49) 19552 - 19557. 10.1073/pnas.1113195108. Green open access

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Abstract

There is considerable interest in how humans estimate the number of objects in a scene in the context of an extensive literature on how we estimate the density (i.e., spacing) of objects. Here, we show that our sense of number and our sense of density are intertwined. Presented with two patches, observers found it more difficult to spot differences in either density or numerosity when those patches were mismatched in overall size, and their errors were consistent with larger patches appearing both denser and more numerous. We propose that density is estimated using the relative response of mechanisms tuned to low and high spatial frequencies (SFs), because energy at high SFs is largely determined by the number of objects, whereas low SF energy depends more on the area occupied by elements. This measure is biased by overall stimulus size in the same way as human observers, and by estimating number using the same measure scaled by relative stimulus size, we can explain all of our results. This model is a simple, biologically plausible common metric for perceptual number and density.

Type: Article
Title: A common visual metric for approximate number and density.
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1073/pnas.1113195108
Publisher version: http://dx.doi.org/10.1073/pnas.1113195108
Language: English
Additional information: Freely available online through the PNAS open access option. PMCID: PMC3241748
Keywords: Algorithms, Discrimination (Psychology), Form Perception, Humans, Models, Psychological, Pattern Recognition, Visual, Psychological Tests, Psychometrics, Task Performance and Analysis, Visual Perception
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Div of Psychology and Lang Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Div of Psychology and Lang Sciences > Clinical, Edu and Hlth Psychology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Div of Psychology and Lang Sciences > Experimental Psychology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Ophthalmology
URI: https://discovery.ucl.ac.uk/id/eprint/1332771
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