Difference magnitude is not measured by discrimination steps for order of point patterns

Protonotarios, Emmanouil D. and Johnston, Alan and Griffin, Lewis D. (2016) Difference magnitude is not measured by discrimination steps for order of point patterns. Journal of Vision, 16 (9). p. 2. ISSN 1534-7362

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Abstract

We have shown in previous work that the perception of order in point patterns is consistent with an interval scale structure (Protonotarios, Baum, Johnston, Hunter, & Griffin, 2014). The psychophysical scaling method used relies on the confusion between stimuli with similar levels of order, and the resulting discrimination scale is expressed in just-noticeable differences (jnds). As with other perceptual dimensions, an interesting question is whether suprathreshold (perceptual) differences are consistent with distances between stimuli on the discrimination scale. To test that, we collected discrimination data, and data based on comparison of perceptual differences. The stimuli were jittered square lattices of dots, covering the range from total disorder (Poisson) to perfect order (square lattice), roughly equally spaced on the discrimination scale. Observers picked the most ordered pattern from a pair, and the pair of patterns with the greatest difference in order from two pairs. Although the judgments of perceptual difference were found to be consistent with an interval scale, like the discrimination judgments, no common interval scale that could predict both sets of data was possible. In particular, the midpattern of the perceptual scale is 11 jnds away from the ordered end, and 5 jnds from the disordered end of the discrimination scale.

Item Type: Article
Keywords: Psychophysics, scaling, discrimination scale, difference scale, signal detection theory, order, regularity, point pattern
Schools/Departments: University of Nottingham UK Campus > Faculty of Science > School of Psychology
Identification Number: https://doi.org/10.1167/16.9.2
Depositing User: Eprints, Support
Date Deposited: 06 Jul 2016 12:50
Last Modified: 23 Sep 2016 09:16
URI: http://eprints.nottingham.ac.uk/id/eprint/34692

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