Fig. 6. Results of feeding experiments. Three groups of animals were trained to discriminate stimuli differing only in the polarisation angle. Asterisks mark choice frequencies differing significantly from chance or from each other (G-tests; *P<0.0001; P<0.005). N gives the number of animals in each test, n gives the number of choices. (A) Tests with the training stimuli (see symbols above and below the diagram, + marks the rewarded pattern, - marks the unrewarded pattern). (B) Choice frequencies for the vertical polarisation angle as function of the intensity ratio between the vertically and horizontally polarised lights. Hatched circles give the polarisation angle and the colour of the training stimulus. (C) Choice frequencies for vertically and horizontally polarised lights of a colour different from the training colour (as in Fig.6A, see symbols above and below the diagram for training and testing stimuli).