Figure 6.  Results of a generalization test given to birds trained to discriminate between two light-sound compounds. The dimmer light and softer sound were correct for R1. The brighter light and louder sound were correct for R2. The top panel shows results obtained from birds that were trained with the smaller light intensity difference. The bottom panel is for birds trained with the larger light intensity difference. For all birds the sound intensity difference was 35 dB.