The mixture gratings consisted of sums of two squarewaves. The qualitative appearance of this type of pattern mixtures, shown using only light and dark shading, is shown in Fig. 2. The patterns were all oriented vertically, and superposition was in sine-phase. Asymmetric matches were obtained using grating sums formed by component squarewaves with different color directions and also by components with the same color direction. A variety of contrast levels was used for each of the components. The same three color directions were used for the squarewave components whether we measured in isolation or as part of a grating mixture.