Figure 1.

Examples of stimulus composition for main experiment, in which one LM phase is combined with two different CM phases. A–C, LM (A) added to CM of the same spatial phase (B) produced an in-phase (0° offset) composite stimulus (C). Note that only the contrast variations about the mean background were added, as detailed in Equation 5. Luminance and contrast modulations (LM and CM) were taken to be in-phase when high- and low-luminance and high- and low-contrast bars of the grating and envelope, respectively, were phase aligned. D, 1D luminance profile corresponding to stimulus image in C. E–H, Same as A–D but the component patterns were summed in antiphase (180° relative phase offset), producing a composite stimulus G in which the high- and low-luminance bars of the grating were centered on the low- and high-contrast bars of the envelope, respectively. See text for further details.