Reject the fixed-pie assumption

Stop assuming your gain must be their loss — most negotiations have hidden joint gains.

Why it works

The "fixed-pie bias" is the default belief that interests are perfectly opposed, which makes people miss compatible interests entirely and settle for worse deals. Consciously assuming there are differences to exploit reorients you from claiming to creating, which is where the extra value comes from.

How to do it

1. Before bargaining, list ways your interests might actually align or differ usefully.
2. Assume joint gains exist until proven otherwise, rather than the reverse.
3. Ask questions aimed at finding differences in priority, not just points of conflict.

Evidence

The fixed-pie bias and its cost are well documented in negotiation research; people routinely overlook compatible and integrative options. Thompson and Hastie found that many negotiators enter assuming interests are directly opposed even when compatible issues exist, and correcting that perception early predicts better joint outcomes. (observational)

Some negotiations really are mostly distributive (e.g. a one-time price with no other variables); win-win isn’t always available.

Sources

• Thompson, L., & Hastie, R. (1990). Social perception in negotiation. Organizational Behavior and Human Decision Processes, 47(1), 98–123.
• Bazerman, M. H., Curhan, J. R., Moore, D. A., & Valley, K. L. (2000). Negotiation. Annual Review of Psychology, 51, 279–314.

Common mistake

Walking in certain it’s zero-sum, which becomes self-fulfilling — you never look for the trades that would have grown the deal.