title: The psychophysics of informal covariation assessment: perceiving relatedness against a background of dispersion.
abstract: The goal of 2 studies was to develop a psychophysical model of informal covariation assessment. The results of Experiment 1 suggest that mean covariation estimates are a function of the ratio of the lengths of the major and minor principal-components axes of correlated bivariate data. In Experiment 2, multidimensional scaling showed that observers perceived (a) the lengths of the major and minor principal-components axes and (b) the slope and dispersion of correlated data. The focal stimulus for mean covariation estimates was the ratio of the major and minor principal-components axes. Moreover, dispersion constituted a background context that lowered estimates somewhat. These results suggested a model of covariation assessment in which mean estimates were mapped onto a product of power transformations of the axis ratio and dispersion of correlated data. This model accounted for 96% of the variability in mean covariation estimates.
authors.affiliation: Department of Psychology, University of Illinois at Urbana-Champaign, USA. boyntond@wcsu.edu
authors.forename: D M
authors.initials: DM
authors.lastname: Boynton
mesh_terms: D003463:Cues; D006801:Humans; D007600:Judgment; D008960:Models, Psychological; D011601:Psychophysics