Make them solve the implementation for you

Ask "What does success look like?" and "How do we get there?" to make the other side do the planning.

Why it works

When the other party names what success looks like and outlines how to get there, they take psychological ownership of the solution. Ownership commitment is far stronger than compliance: they will work to make the plan succeed because it is now theirs. The process also surfaces hidden constraints and reveals real interests, which is more useful intelligence than any concession.

How to do it

1. After reaching rough agreement on a goal, ask: "What does success look like on your end?"
2. Then ask: "How do we make sure we get there?"
3. Reflect their answers back to confirm understanding, then let them elaborate further.
4. Take notes — their answers are a map of what they actually need, often different from what they demanded.

Evidence

The ownership effect — greater commitment to self-generated solutions — is supported by research on self-determination and on IKEA-effect-style findings: effort and authorship increase perceived value and commitment to outcomes. (mechanistic)

The IKEA effect study is about assembly and effort; extrapolating to negotiation planning is principled but the direct application is practitioner inference rather than a studied outcome.

Sources

• Norton, Mochon & Ariely (2012), the IKEA effect: when labor leads to love, Journal of Consumer Psychology

Common mistake

Taking over the planning once you get the information you wanted — the point is to let them author the solution, not to harvest their input and then impose yours.