Assimilation effects are most often observed in displays containing high spatial frequency patterns (Helson,
1963; Smith, Jin, & Pokorny,
2001); however, other factors such as the width of the inducing contour (Fach & Sharpe,
1986) or the luminance relationships within the stimulus can also influence whether assimilation is observed (Cao & Shevell,
2005; De Weert & Spillmann,
1995; Hamburger,
2005; Helson,
1963; Wook Hong & Shevell,
2004). As with other assimilation patterns, the strength of the WCE decreases with increasing edge width (Pinna et al.,
2001) and induced area (Devinck, Delahunt, Hardy, Spillmann, & Werner,
2006) or increases with the luminance contrast between the two double contours (Devinck, Delahunt, Hardy, Spillmann, & Werner,
2005). These variables are also known to influence the strength of color contrast tested under a wide range of conditions (Krauskopf, Zaidi, & Mandler,
1986; Ware & Cowan,
1982; Zaidi, Yoshimi, Flanigan, & Canova,
1992). Factors such as the chromatic composition of the inducing field have been systematically explored in color contrast (Barnes, Wei, & Shevell,
1999; Jameson & Hurvich,
1959; Kinney,
1962; Tiplitz-Blackwell & Buchsbaum,
1988; Valberg,
1974) but not in color assimilation.