Fig. 2. Results of Expt 1, colour discrimination. Bees were trained with a blue square (positive) versus a yellow square (negative) presented on a white background. The trained bees are then tested with various pairs of coloured triangles as specified along the abscissa; bl, blue; yel, yellow; gr, green; viol, violet. The bars showing the choice frequencies (Cfs) obtained in favour of each of the two triangles are coloured accordingly. The total number of choices (N) recorded with each pair of triangles is given above each pair of bars.