Figure 1.
Physical robots and neural network controller.
(A) The Alice robots used in the experiments were equipped with infrared distance sensors (IR) and vision sensors (camera). (B) The input neurons (small circles) of the artificial neural network were connected to internal and output neurons (large circles) by 33 connection weights (lines connecting circles).
Figure 2.
Mean group foraging efficiency during the 500 generations of selection.
Lines represent the mean number of items transported successfully for each of the 25 treatments (five relatedness values × five c/b ratios, 20 replicates per treatment), with yellow dashed lines representing treatments where r = c/b, red lines treatments where r < c/b, and blue dotted lines treatments where r > c/b.
Figure 3.
Mean level of altruism during the 500 generations of selection.
Lines represent the mean level of altruism, defined as the proportion of food items shared with other group members, for each of the 25 treatments (five relatedness values × five c/b ratios, 20 replicates per treatment), with yellow dashed lines representing treatments where r = c/b, red lines treatments where r < c/b, and blue dotted lines treatments where r > c/b.
Figure 4.
Mean level of altruism at the end of the 500 generations of selection.
The mean (±SD) level of altruism as a function of the c/b ratio and level of relatedness (20 replicates per treatment) for r = c/b (yellow lines), r < c/b (red lines), and r > c/b (blue lines). Dashed lines are fits based on a model by McNamara et al. [44]–[46].
Table 1.
Effects of a single mutation on performance, altruism, and both.