Chris Voss 65-85-95-100 Ackerman model: rehearse the official sequence

Drill the official four-bid Ackerman sequence — 65%, 85%, 95%, then 100% of your target — out loud in advance, so you execute it under pressure.

Why it works

High-stakes negotiation produces cognitive and emotional load that degrades in-the-moment decision-making. The Ackerman model as Voss publishes it in Never Split the Difference is a fixed four-bid ladder: set your target, open at 65% of it, then 85%, then 95%, then 100%. The increments shrink by design — 20 points, then 10, then 5 — so each concession reads as smaller than the last and signals you are approaching a real limit. Two details make the sequence work and are the ones people drop: use precise non-round numbers (37,893 rather than 38,000), because a specific figure implies a calculation behind it rather than a position to be haggled; and on the final 100% bid, add a non-monetary item you know the counterpart cannot easily grant, which makes the number itself feel like the end of the road. Rehearsing the numbers, the counteroffer responses, and the calibrated questions moves them into procedural memory, freeing working memory for reading the counterpart and adapting. The preparation is the source of the poise that experienced negotiators display.

How to do it

1. Set your target number first — the full 100% you actually want — then compute the ladder from it.
2. Write out your 65% / 85% / 95% / 100% bids with your real figures, and make each one a precise non-round number rather than a rounded one.
3. Plan a calibrated "how am I supposed to do that?" style response for each of the three most likely counteroffers, so you invite them to solve the gap instead of conceding into it.
4. Decide in advance the non-monetary item you will attach to the final 100% bid — something the counterpart is unlikely to be able to give.
5. Practice saying your numbers and empathy phrases aloud — in-person delivery of specific numbers requires fluency that reading does not build.
6. Debrief after each negotiation to refine the sequence for future use.

Evidence

Research on mental simulation and behavioral rehearsal shows that imagining and rehearsing actions improves subsequent performance under pressure — reducing the cognitive cost of execution and improving adaptive response to surprises. (observational)

Rehearsal builds fluency for planned scenarios; it does not prepare you for genuinely novel developments. Flexibility alongside preparation is the goal.

Sources

• Taylor & Pham (1996), mental simulation and goal attainment, Journal of Personality

Common mistake

Treating negotiation preparation as only research on the deal terms — the behavioral and verbal rehearsal is where the preparation translates into actual performance.