Summary
Making the first offer usually helps you.
A very aggressive first offer makes the deal more likely to fail.
The more issues on the table, the less the first number matters.
Every mediation reaches the same moment. The opening statements are over, the issues are on the table, and someone has to name a number.
Lawyers, mediators, and negotiation researchers have argued for decades about whether it pays to go first or to wait. A 2025 study finally gives a clear answer, built on data from more than 16,000 people.
Going first helps. How high you open matters even more. And the number of issues in the dispute changes how much any of it matters.
What the Researchers Did
The study, The Power and Peril of First Offers in Negotiations: A Conceptual, Meta-Analytic, and Experimental Synthesis, was led by Hannes M. Petrowsky of Leuphana University.
The 15-author international team included Martin Schweinsberg, an associate professor of organizational behavior at ESMT Berlin. The paper appeared in the November 2025 issue of Organizational Behavior and Human Decision Processes, a peer-reviewed journal.
The core of the work is a meta-analysis, a study that combines results from many earlier studies. The authors pooled 374 effects from 90 studies, covering 16,334 people. They then ran two new, pre-registered experiments with 2,121 more participants.
The research covered negotiations in general, not mediation. I read it as applying to mediation, and I think the fit is close because mediation is a negotiation with a neutral in the room.
The authors are candid about the gaps. They want more research on real negotiations, such as union and political talks, and more studies that report the deals that fell apart, not only the ones that closed.
Going First Usually Wins
Across the pooled data, the person who made the first offer usually ended up with a better result. Ambitious first offers also beat moderate ones, and higher openers tended to produce better final agreements.
ESMT Berlin's announcement puts a figure on it: in 81% of the negotiations examined, higher first offers led to better final outcomes for the person who made them.
The effect sizes tell a sharper story. On the paper's standardized scale (Hedges' g), going first was worth 0.42. Opening ambitiously instead of moderately was worth 1.14, more than twice as much. The order matters less than the number.
The reason is anchoring.
The first number becomes the reference point everyone reacts to, and many participants respond to it without being aware of it. A party who waits for the other side to open lets the other side set that reference point.
When an Aggressive Number Backfires
Ambitious first offers led to fewer deals. More negotiations ended in an impasse, with no agreement at all, and the people on the receiving end were less satisfied with the negotiation.
On the same scale, impasses rose by 0.42, and the recipient's satisfaction fell by 0.40. Those penalties are about as large as the gain from going first.
A one-time sale ends at signing. Mediation often does not. Business partners still run the company together. Co-parents still share a calendar. Employers and employees may keep working side by side.
The ESMT Berlin summary makes a related point about deals where work continues after the agreement: a party who feels they clearly lost may later give less speed, quality, or effort.
An ambitious opener buys a better deal if one closes, and lowers the odds that one does. In mediation, that is the trade every party makes when they name a number.
Why Complex Disputes Are Different
The study found that first offers have smaller effects when a negotiation involves many issues, and the psychological reasons behind those effects change.
Most mediations are multi-issue negotiations.
A business dispute can turn on the amount, payment terms, timing, and confidentiality. A family mediation can cover support, property, and a custody schedule.
With many issues on the table, a single number has less pull.
Going first still did not hurt. The advantage shrank as issues piled up, but it did not flip into a disadvantage. The ESMT Berlin summary adds that in these situations, the relationship and a creative search for solutions that work for both sides carry more weight.
What This Means If You Are Heading Into Mediation
Four practical steps follow from the findings.
Do your homework before you name a number. ESMT Berlin's summary says negotiators who make the first offer and arrive well prepared generally get better outcomes. An opening number you cannot explain gives the other side a reason to walk.
Aim high, not extreme. Ambitious openers produced the biggest gains in the data, and also more impasses and less satisfied counterparts. Set a realistic range first, then open near the top of it with a number you can defend.
Weigh the relationship before you open. If you will keep dealing with the other side as a co-parent, partner, or employer, their view of the deal matters after the session. Open lower than you would in a one-time deal.
In a multi-issue dispute, plan the package, not just the number. Going first still did not hurt in complex U.N. negotiations, but the edge was smaller. Decide in advance which issues you can trade, and do not spend the session defending one opening figure.
What a Good Mediator Does With an Aggressive Opening
An aggressive opening does not have to end the session. In my experience, a good mediator handles it in three ways.
First, the mediator acknowledges the number without reacting to it.
Second, the mediator moves the conversation away from the single figure and toward interests and the other open issues. That matches what the research found: the more issues in play, the less one number controls the result.
Third, the mediator reality-tests in private caucus. Asking a party how they would explain the number to a judge, or what happens if the other side leaves, lets them adjust without losing face in front of the other side.
Frequently Asked Questions
Should I make the first offer in mediation?
In most cases, yes. The study found that the person who makes the first offer usually ends up with a better result, and going first did not hurt even in complex negotiations.
How high should my first offer be?
Ambitious, but defensible. The data show that opening ambitiously mattered more than going first, but ambitious openers also led to more failed deals and left the other side less satisfied. Open near the top of a realistic range you can justify.
Can an aggressive first offer end a mediation?
Yes. The study found that ambitious first offers led to more impasses, meaning more negotiations ended with no agreement. A mediator's job at that point is to acknowledge the number calmly and reality-test it in private.
Does the first offer matter in a divorce or family mediation? In
It matters less than in a single-issue dispute. The study found that first offers have smaller effects when many issues are on the table, and a family mediation covering support, property, and a custody schedule is that kind of negotiation.
What is anchoring in negotiation?
Anchoring means the first number becomes the reference point everyone reacts to. ESMT Berlin's summary of the study notes that many participants respond to that first figure without realizing it.
Sources
Petrowsky, H. M., et al. "The Power and Peril of First Offers in Negotiations: A Conceptual, Meta-Analytic, and Experimental Synthesis." Organizational Behavior and Human Decision Processes, Vol. 191, November 2025 (published online September 19, 2025). https://doi.org/10.1016/j.obhdp.2025.104448
Full study (free PDF), Leuphana University publication repository, November 2025. https://pubdata.leuphana.de/entities/publication/29dc7e5d-01eb-420a-b73d-66e0be7cd440
ESMT Berlin press release via idw, "ESMT Berlin study: What makes a first offer successful in negotiations," December 18, 2025. https://idw-online.de/en/news863681