Pinker takes the idea of the “bystander effect” (when people don’t help someone in distress) and reframes it through game-theory: he shows how the Volunteer’s Dilemma occurs when multiple bystanders each hope someone else will intervene — and as the number of potential helpers grows, the chance any one helps drops.

• The core insight: when someone needs help, each individual faces a trade-off — help and bear a cost, or wait and risk no one helping. Pinker shows that rational reasoning about what others might be thinking leads to diffusion of responsibility.
• I was particularly struck by how Pinker emphasizes common knowledge — not just “everyone knows there’s someone in trouble”, but “everyone knows that everyone knows” and so on. That recursive awareness (or lack thereof) really changes behaviour.
• The experiment he reports on: when knowledge of the need to act is broadcast publicly (common knowledge) vs privately (just one person knows) — volunteering declines as group size increases under common knowledge.
• This is quite commonly observed as the number of members in an organization grows, the productivity declines, and most of the time is spent on information transfer at different levels.

So, now that I've read it, I believe the best action to take in such situation is to self-volunteer and not wait for others to make the sacrifice. It might come at a cost - be it financial, emotional or physical, but what I think one should do is help anyone in need, because there are only three possibilities for any bystander:

1. Best Case: Someone else will volunteer for the task.
2. Worst Case: No one will volunteer.
3. Average Case: self-volunteer.

And thus for the sake of humanity, please be the self-volunteer.