Table 1.
An overview of all possible pure strategies that condition their behaviour on the previous interaction. (The four columns on the left show whether the strategy cooperates (1) or defects (0), for each of the four possible outcomes of the previous interaction (from left to right: mutual cooperation, having cooperated while the opponent defected, having defected while the opponent cooperated, and mutual defection). The column on the right shows the name of the strategy that is used to refer to them in the main text. The two middle columns show the percentage of the genotype space that is associated with each strategy for the two different behavioural architectures. These percentages were obtained by generating a large number of genotypes (in the same way as generating a genotype through ‘entire-genome mutation’), and subsequently determining the strategy induced by each genotype (as explained in the electronic supplementary material).)
| behaviour |
percentage of genotype space |
||||||
|---|---|---|---|---|---|---|---|
| CC | CD | DC | DD | 1 : 1 mapping | neural network | strategy name | strategy description |
| 0 | 0 | 0 | 0 | 6.25 | 40.35 | ALLD | always defects |
| 0 | 0 | 0 | 1 | 6.25 | 1.79 | desperate | only cooperates after mutual defection |
| 0 | 0 | 1 | 0 | 6.25 | 1.75 | Acon-D | anti-conventional, shifts after playing opposite of opponent, otherwise defects |
| 0 | 0 | 1 | 1 | 6.25 | 1.65 | inconsistent | plays opposite of previous move |
| 0 | 1 | 0 | 0 | 6.25 | 1.75 | con-D | conventional, stays after playing the opposite of opponent, otherwise defects |
| 0 | 1 | 0 | 1 | 6.25 | 1.65 | ATFT | anti-tit for tat, plays opposite of opponent's last move |
| 0 | 1 | 1 | 0 | 6.25 | 0.08 | APavlov | win, shift; lose, stay |
| 0 | 1 | 1 | 1 | 6.25 | 0.98 | hopeless | only defects after mutual cooperation |
| 1 | 0 | 0 | 0 | 6.25 | 0.98 | grim | only cooperates after mutual cooperation |
| 1 | 0 | 0 | 1 | 6.25 | 0.08 | Pavlov | win, stay; lose, shift |
| 1 | 0 | 1 | 0 | 6.25 | 1.65 | TFT | tit for tat, copies opponent's last move |
| 1 | 0 | 1 | 1 | 6.25 | 1.75 | MNG | Mr Nice Guy, only defects after ‘being cheated’ (playing C while other plays D) |
| 1 | 1 | 0 | 0 | 6.25 | 1.65 | consistent | repeats its own previous move |
| 1 | 1 | 0 | 1 | 6.25 | 1.75 | con-C | conventional, stays after playing the opposite of opponent, otherwise cooperates |
| 1 | 1 | 1 | 0 | 6.25 | 1.79 | willing | only defects after mutual defection |
| 1 | 1 | 1 | 1 | 6.25 | 40.35 | ALLC | always cooperates |