yefreitor's Quick takes

Claim: Credible plans for a "pivotal act" may drive AI race dynamics

(Epistemic status: I had mathematica do all the grunt work and did not check the results carefully)

Consider a simple normal-form game with two equally capable agents A and B, each of which is deciding whether to aggressively pursue AI development, and three free parameters:

• the probability $p_{doom}$ that accelerating AI development results in an existential catastrophe (with utility -1 for both agents, versus a utility 0 status quo). 
• the utility $u_1$ of developing the first friendly AI
• the utility $-1<u_2<u_1$ of the other agent developing friendly AI

We'll first assume the coin only gets flipped once: developing a friendly AI lets you immediately control all other AI development.

Since our choice of parameterization was in retrospect one that requires a lot of typing, we'll define $u_{+}=\frac{u_1+u_2}{2}$, $u_{-}=u_1-u_{+}=u_{+}-u_2$ and then rescale to get something more readable

$\begin{array}{ccc}& \text{Accelerate}& \text{Don't}\\ \text{Accelerate}& u_{+}& u_{+}-u_{-},u_{+}+u_{-}\\ \text{Don't}& u_{+}+u_{-},u_{+}-u_{-}& \frac{p_{doom}}{1-p_{doom}}\end{array}$

• (Accelerate, Accelerate) is always a Nash equilibrium, no matter how trivial the differences $u_{-}$ captures are.
• (Don't, Don't) is a Nash equilibrium when $(u_{+}+u_{-})(1-p_{doom})<p_{doom}$, as you would expect
• (Don't, Don't) is never a trembling-hand equilibrium, since (Don't) does not weakly dominate (Accelerate) for either player.
• When $(u_{+}+u_{-})(1-p_{doom})\ge p_{doom}$ (Accelerate) weakly dominates (Don't) and (Accelerate, Accelerate) is a trembling-hand equilibrium.

Now consider the case where (Accelerate, Accelerate) instead flips two coins.

$\begin{array}{ccc}& \text{Accelerate}& \text{Don't}\\ \text{Accelerate}& u_{+}(1-p_{doom})-p_{doom}& u_{+}-u_{-},u_{+}+u_{-}\\ \text{Don't}& u_{+}+u_{-},u_{+}-u_{-}& \frac{p_{doom}}{1-p_{doom}}\end{array}$

This is potentially a much safer situation:

• (Accelerate, Accelerate) is only a Nash equilibrium when $p_{doom}<\frac{u_{-}}{u_{+}+1}$
• (Don't, Don't) is still a Nash equilibrium when $(u_{+}+u_{-})(1-p_{doom})<p_{doom}⟺p_{doom}>\frac{u_{+}+u_{-}}{u_{+}+u_{-}+1}$
• (Don't, Don't) is a trembling-hand equilibrium if it's a Nash equilibrium and (Accelerate, Accelerate) is not.