Posted in Psychology & Medicine

## Tit For Tat

In human society, there are many ways for a person to interact with others when in a group setting. Some may choose to be selfish and only be out for their best interests, while others may choose altruism and cooperate with each other. The mathematical model that tries to predict human behaviour and outcome in these settings is the Prisoner’s Dilemma – the core of game theory. Tit for tat is one strategy that can be employed in such a setting.

The basis of tit for tat is equivalent exchange. A tit for tat player always chooses to cooperate unless provoked. As seen in the Prisoner’s Dilemma, if both players cooperate, both benefit (let us say 3 points each); if one player defects, that person gains more than from cooperation (5 points) while the tit for tat player gains 0 points.
If a tit for tat player is provoked, that player will retaliate. However, the player is also quick to forgive. Ergo, if the other player chose to cooperate, the tit for tat player (following the principle of equivalent exchange), will also cooperate. If the other player defected, the tit for tat player loses the first round and then chooses to defect from then on.
Note that tit for tat strategy only works when there is more than one game so that the player has a chance to retaliate.

Let us use an example to illustrate why tit for tat strategy works. In this scenario, two tit for tat players and two defectors all play six games each, using the above point system (if both defect, they each receive 1 point). The results are as follows:
• Tit for tat vs defector: Tit for tat loses first round, both defect for next 5 rounds (5 vs 10)
• Tit for tat vs tit for tat: Both cooperate on every round (18 vs 18)
• Defector vs defector: Both defect on every round (6 vs 6)

When the points are added up, a tit for tat player gains 28 points (5 + 5 + 18) while a defector only gains 26 points (6 + 10 + 10). This is a surprising turn of events, as the defectors never lost a round and tit for tat players never “won” a round. This goes to show how cooperation leads to better long-term results while selfishness prevails.

There are shortcomings of this strategy. If there is a failure in communication and one tit for tat player mistakes the other’s actions as an “attack”, they will retaliate. The other player then retaliates to this and a vicious cycle is formed. This is the basis of many conflicts ranging from schoolyard fights to wars (although interestingly, tit for tat strategy is also found during wars in the form of “live and let live”). One way to prevent this is tit for tat with forgiveness, where one player randomly cooperates to try break the cycle (a defector would respond negatively while a tit for tat player will accept the cooperation), or the tit for two tats, where the tit for tat player waits a turn before retaliating, giving the opponent a chance to “make up for their mistake”.

Computer simulations have all proven that tit for tat strategy (especially the other two types mentioned just before) are extremely effective in games. In fact, it is considered one of the most optimal strategies in overcoming the Prisoner’s Dilemma.

In human societies, there is usually a mix of “nice people” and “selfish people”. By cooperating and trusting each other, we can produce a much greater gain over time compared to being selfish. And since society still unfortunately has “defectors”, you can retaliate to those who refuse to cooperate by defecting on them also. Ergo, a good approach to life is to initially reach out your hand to whoever you meet and treat them from there on according to how they respond. If they take your hand and want to cooperate, treat them with altruism and help them out. If they swat your hand away and try to use you for their selfish gain, it is fine to shun them and not help them out.

Through cooperation, understanding and connection, we can build a far more productive and efficient society, just like the ants.