Experimental set-up. Schematic of the set-up. (a,b) BEE and BEC bees were placed frontally relative to the monitor. (c,d) REE and LEE bees were rotated by 60° to make the right or the left eye face the monitor. The red colour indicates the covered eye(s).

Mean learning performances for four five-trial blocks (the two original 10-trial blocks are split into two each for a clearer presentation). BEC bees show 0% learning performance throughout the entire training. The BEE bees' performance rises steadily, with a mean response rate of 39% in the last five trials. REE bees also show an increase in learning performance, but the response rate is slightly (never significantly) lower than that of BEE bees throughout the training. In the last five trials REE bees show a performance level of 33%. LEE bees reach a mean learning performance of only 13%, which is significantly lower than that of BEE and REE groups. LEE bees perform already significantly worse than BEE and REE bees in trials 6–10. Stars indicate statistical difference (p<0.001). Open stars indicate that BEE and REE bees are not statistically different from each other; filled stars indicate that LEE bees are statistically different from BEE and REE bees in trials 6–10 and from BEE bees in trials 11–15. N, overall number of bees in the group; n, average number of total responses during training. The bars plotted show standard errors of the means.