“…Numerous studies on visual masking using unnatural masks have shown that thresholds can be affected by controlled, often low-level mask properties. For example, thresholds have been shown to be affected by changes in contrast (e.g., Legge & Foley, 1980;Watson & Solomon, 1997), changes in luminance (e.g., Peli, 1990;Watson, 1993a;Eckert & Bradley, 1998), changes in pattern or noise properties (e.g., Ahumada, 1967;Legge, Kersten, & Burgess, 1987;Delord, 1998;Nadenau & Reichel, 2000;Winkler & Susstrünk, 2004), and changes in subject familiarity .…”