[Question] Open problem: how can we quantify player alignment in 2x2 normal-form games?

In my experience, constant-sum games are considered to provide “maximally unaligned” incentives, and common-payoff games are considered to provide “maximally aligned” incentives. How do we quantitatively interpolate between these two extremes? That is, given an arbitrary payoff table representing a two-player normal-form game (like Prisoner’s Dilemma), what extra information do we need in order to produce a real number quantifying agent alignment?

If this question is ill-posed, why is it ill-posed? And if it’s not, we should probably understand how to quantify such a basic aspect of multi-agent interactions, if we want to reason about complicated multi-agent situations whose outcomes determine the value of humanity’s future. (I started considering this question with Jacob Stavrianos over the last few months, while supervising his SERI project.)


  • Assume the alignment function has range or .

    • Constant-sum games should have minimal alignment value, and common-payoff games should have maximal alignment value.

  • The function probably has to consider a strategy profile (since different parts of a normal-form game can have different incentives; see e.g. equilibrium selection).

  • The function should probably be a function of player A’s alignment with player B; for example, in a prisoner’s dilemma, player A might always cooperate and player B might always defect. Then it seems reasonable to consider whether A is aligned with B (in some sense), while B is not aligned with A (they pursue their own payoff without regard for A’s payoff).

    • So the function need not be symmetric over players.

  • The function should be invariant to applying a separate positive affine transformation to each player’s payoffs; it shouldn’t matter whether you add 3 to player 1′s payoffs, or multiply the payoffs by a half.

  • The function may or may not rely only on the players’ orderings over outcome lotteries, ignoring the cardinal payoff values. I haven’t thought much about this point, but it seems important. EDIT: I no longer think this point is important, but rather confused.

If I were interested in thinking about this more right now, I would:

  • Do some thought experiments to pin down the intuitive concept. Consider simple games where my “alignment” concept returns a clear verdict, and use these to derive functional constraints (like symmetry in players, or the range of the function, or the extreme cases).

  • See if I can get enough functional constraints to pin down a reasonable family of candidate solutions, or at least pin down the type signature.