Fig. 6. Results of (A) Expt 4 and (B) Expt 5. Two pairs of randomly patterned convex shapes were used in two separate training experiments (A and B), presenting the shapes 50 mm in front of a patterned background (i, top). The shapes are shown separately for better visibility (i, middle). In this situation, bees could use only motion contrast for recognizing the shapes. When the distance between shapes and background is eliminated (i, bottom), bees cannot tell the two shapes apart. The trained bees are then tested using the outlines or fragments of the outlines of the two training shapes (ii–viii). Choice frequency (CF) and N-values are given for each test. Results of reciprocal training experiments (not illustrated) were very similar.