Local versus global contrasts in texture segregation

In a texture pair (TP) yielding a vertical or horizontal edge, the local (l uminance or color) contrast or the local orientation of the individual text els is traded off with the global strength of the luminance-, color-, or or ientation-defined TP edge so as to keep the latter at the detection thresho ld. Local and global contrasts are defined along the same (within-domain co nditions) or along distinct physical dimensions (transdomain conditions). I n the latter case local luminance or color contrast is traded off against g lobal orientation. In all cases TP's are presented for 66.7 or 333.3 ms. Te xtels differ from the background in either luminance or color so that the T P's are respectively equichromatic or equiluminant. TP edge strength is mod ulated by means of swapping variable proportions of textels between the two textures in the TP. The observed local-global relationships are fitted wit h a version of the equivalent noise model for contrast coding modified to i nclude the presentation time factor. The extension of the standard model in the time domain is meant to allow comparison between equivalent noise esti mates for variable duration stimuli. Model fits of the within-domain data y ield equivalent noise energy values significantly different for color- and luminance-defined TP's but are not applicable for the transdomain experimen ts, which indicates that global orientation processing is independent of bo th local luminance and local color contrast insofar as the latter are above the detection threshold. Finally, this study points to the equivalence amo ng the local-global, the equivalent noise, and the statistical approaches t o texture segregation. (C) 1999 Optical Society of America [S0740-3232(99)0 2003-7].