Table 2. This table summarises all the available PD strategies used in the literature.

Strategy name	Description
Always Cooperate	Cooperates in each round.
Always Defect	Defects in each round.
Random	50% of cooperation or defection.
Tit for tat	Starts with cooperation and then the design replicate the opponents’ previous move.
N% Forgiving or Generous tit for tat	‘Tft’ with N percentage of cooperating after opponent’s defection.
Tit for N tats	‘Tft’ with cooperating until N number of consecutive opponent’s defections is reached.
Pavlov or Win-stay-Lose-swift	Switch choice whenever receives S or P payoffs.
Suspicious tit for tat	Like ‘tft’ but as ‘wsls’ does not swift on T payoff.
Rilling et al. (2002)	Cooperation in first round, defection in last three, else, decision based on last two players’ choices.
Rilling et al. (2004b)	50% possibility of reciprocate cooperation and always reciprocate defection.
Rilling et al. (2012)	For player A: 90% reciprocates defection and 67% reciprocates cooperation. For player B, ‘tft’ with 33% of cooperation after mutual defection, 10% of cooperation after unilateral (own) defection and always defection after two consecutive rounds of unilateral (own) defection.
McClure et al. (2007) (based on Rilling et al., 2002)	Cooperation in the first round, defection in the last two, 50% possibility of defection after four consecutive mutual cooperation rounds. Else, the decision is based on the player’s last two choices.
Zero Determinant (ZD) strategies (Press & Dyson, 2012)	Each decision is determined by the probabilities of cooperation based on the four possible choice combinations of the previous round.

Note:

A brief description of the key elements of each strategy is presented in this table. The impact that each strategy could have on the PD outcome is presented in the ’Strategy’ section of our review.