Calculation efficiencies for mean numerosity

Solomon, J. A. & Morgan, M. J. (2018). Calculation efficiencies for mean numerosity. Psychological Science,

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Relative numerosity is traditionally studied using texture pairs. Observers must decide which member of each pair has the greater total number of texture elements. Our textures were segregated into non-overlapping “sectors” containing between 0 and 4 elements, and our observers were asked to select the texture containing the greater average number of texture elements (i.e. per sector). If observers were more sensitive to total numerosity than average numerosity, their performances (quantified by the just-noticeable Weber fraction) should have been better when the two textures occupied the same number of sectors than when they occupied unequal numbers of sectors. However, we recorded Weber fractions between 11 and 13% for all observers in all conditions. These performances were comparable with an otherwise-ideal observer whose decisions were based on between 3 and 5 sectors in each texture. We conjecture that traditional numerosity discriminations are based on similarly small numbers of element clusters.

Item Type: Article
Additional Information: Solomon, J.A. & Morgan, M. J., Calculation efficiencies for mean numerosity, Psychological Science pp. xx-xx. Copyright © 2018 Sage. Reprinted by permission of SAGE Publications.
Subjects: R Medicine > RE Ophthalmology
Divisions: School of Health Sciences > Department of Optometry & Visual Science

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