“…A number of studies have investigated detection of “first-order” luminance step boundaries (Elder & Sachs, 2004; McIlhagga & May, 2012; McIlhagga, 2018; McIlhagga & Mullen, 2018), as well as detection and segmentation of “second-order” texture boundaries having no luminance difference but differences in texture contrast (Dakin & Mareschal, 2000; DiMattina & Baker, 2019), density (Zavitz & Baker, 2014), orientation (Wolfson & Landy, 1995), polarity (Motoyoshi & Kingdom, 2007) or phase (Hansen & Hess, 2006). However, the segmentation of first-order luminance texture boundaries, and the underlying computations, are poorly understood.…”