Dickinson, J. EdwinBell, JasonBadcock, David Russell2015-11-242015-11-241932-6203http://hdl.handle.net/1885/16708Observers make sense of scenes by parsing images on the retina into meaningful objects. This ability is retained for line drawings, demonstrating that critical information is concentrated at object boundaries. Information theoretic studies argue for further concentration at points of maximum curvature, or corners, on such boundaries [1]-[3] suggesting that the relative positions of such corners might be important in defining shape. In this study we use patterns subtly deformed from circular, by a sinusoidal modulation of radius, in order to measure threshold sensitivity to shape change. By examining the ability of observers to discriminate between patterns of different frequency and/or number of cycles of modulation in a 2x2 forced choice task we were able to show, psychophysically, that difference in a single cue, the periodicity of the corners (specifically the polar angle between two points of maximum curvature) was sufficient to allow discrimination of two patterns near their thresholds for detection. We conclude that patterns could be considered as labelled for this measure. These results suggest that a small number of such labels might be sufficient to identify an object.Funding came from Australian reserch council grants DP0666206, DP1097003 and DP110104553 to DRB and DP110101511 to JB, www.arc.gov.au. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript© 2013 Dickinson et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.discrimination (psychology)humanspattern recognition, visualphotic stimulationdifferential thresholdNear Their Thresholds for Detection, Shapes Are Discriminated by the Angular Separation of Their Corners2013-05-3110.1371/journal.pone.00660152015-12-11