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Why do both prisoners confess in the prisoner’s dilemma?

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A colorful payoff matrix for a normal form game in game theory, showing strategy options-support, oppose, evade-for both party A and party B. Each cell contains cartoon figures representing each party's action and lists percentage payoffs for A and B. The bottom-right cell is labeled saddlepoint, highlighting the equilibrium. — game theory Table 1
The normal-form table illustrates the concept of a saddlepoint, or entry, in a payoff matrix at which the expected gain of each participant (row or column) has the highest guaranteed payoff.

In the prisoner’s dilemma, both prisoners confess because it is the dominant strategy for each individual, despite the fact that it leads to a worse collective outcome than if both had remained silent.12

Because the game is noncooperative—meaning the prisoners cannot make binding agreements—each player acts in their own self-interest to minimize their own prison sentence. When analyzing the decision:32

If the other prisoner confesses, confessing results in a shorter sentence than remaining silent.2
If the other prisoner remains silent, confessing results in immediate release rather than a short prison term.12

Since confessing provides a better outcome for a prisoner regardless of what the other does, both choose to confess. This outcome is known as the Nash equilibrium, a state where no player can improve their own payoff by unilaterally changing their strategy. While both would be better off if they cooperated by remaining silent, the lack of trust and inability to enforce an agreement traps them in this mutually disadvantageous result.243