Abstract
Previous studies have shown that texture regularity is adaptable, and have suggested that texture regularity might be coded by the peakedness of the underlying spatial frequency distribution. Here we demonstrate the related phenomenon of simultaneous regularity contrast (SRC), in which the perceived regularity of a central texture is influenced by the regularity of a surrounding texture. We presented center-surround arrangements of textures and measured the perceived regularity of the centre, using a centre-only comparison stimulus and a 2AFC procedure. From the resulting psychometric functions the SRC was measured as the difference between test and comparison regularity at the PSE (point of subjective equality). Observers generally exhibited asymmetric bidirectional SRC, in that more regular surrounds decreased the perceived regularity of the centre by between 20–40%, while less regular surrounds increased the perceived regularity of the centre by about 10%. Consistent with previous studies, a wavelet spatial frequency (SF) analysis of the stimuli revealed that their SF distributions became sharper with increased regularity, and therefore that distribution statistics such as kurtosis and SF bandwidth might be used to code regularity.
Highlights
Texture regularity, i.e. the degree of orderliness of element positions in a texture (“regularity”) is a basic texture property
Note that regularity defined in relation to a lattice of element positions is different from the classical “symmetries” - mirror symmetry, radial symmetry, and translational symmetry[9,10,11,12,13]
psychometric function (PF) and point of subjective equality (PSE) for each condition were calculated from the data collected for each observer
Summary
I.e. the degree of orderliness of element positions in a texture (“regularity”) is a basic texture property. A simple and commonly employed method to construct textures of varying regularity levels is to apply random perturbation (“jitter”) independently to the horizontal and vertical element positions in a notional lattice pattern of texture elements, e.g. dots - a larger range of the jitter gives more irregular textures[6,7,8]. Following on from Ouhnana et al.’s8 analysis of the Fourier composition of texture regularity, Jennings and Kingdom[14] suggest that information about regularity and translational symmetry is likely carried by the Fourier amplitude spectrum whereas information about mirror- and radial-symmetry is likely carried by the Fourier phase spectrum This idea is in keeping with the finding that regularity information is mostly preserved under Fourier phase scrambling[15] and that the perception or discrimination of regularity does not require the encoding of the relative position of each texture element[16]. This could be explained by element proximity, which is a much stronger cue for contour detection, because there are more close local pairings of elements in random placements than in regular ones[22]
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