Bluffing and Lying in Contract Negotiations: What New Research Says

A supplier says another customer will take the remaining capacity by Friday. A buyer says several alternatives are under review. One side insists that a deadline cannot move. The other says approval above a certain number is impossible.

Anyone who negotiates often knows that these statements do not all deserve the same treatment. Some describe facts that can be checked. Some describe internal limits that are difficult to verify. Some are deliberately incomplete. Some may simply be false.

A study published on 7 September 2026 in Negotiation and Conflict Management Research adds an interesting layer to that problem. Stefanie Jung, Lina María Gélvez Álvarez and Peter Krebs compared how students, judges, lawyers and professional negotiators judged lies in contract negotiations and what they expected the law to condemn. Professional experience appeared to shape those expectations. Moral judgments were less uniform.

The paper does not provide procurement with a new licence to bluff, nor does it offer a legal rule for commercial negotiations in every jurisdiction. Its practical value is elsewhere. It reminds us that experienced people tend to enter negotiations with a more complicated understanding of strategic communication than the simple advice to "trust the other side" or "never believe anything" suggests.

The useful boundary is between privacy and false fact

Commercial negotiations require private information. A supplier is not expected to disclose its reservation price. A buyer normally does not reveal the maximum approved budget. Neither side has to explain every internal weakness or say exactly how badly it needs the deal.

That privacy creates room for positioning. "This is the lowest number I can approve today" may be a statement about today's authority rather than the lowest price the company could ever accept. "We are considering alternatives" can describe anything from an active competitive process to an early internal review.

The statement changes character when it becomes a concrete factual claim. "Our steel input increased 18 percent this quarter" can be checked against an index and a cost structure. "We have no capacity after Friday" can be explored through delivery dates, allocation rules and the consequences of waiting. An invented competing quotation is different again because it fabricates evidence rather than withholding information.

For a buyer, this classification matters more than trying to decide whether the person across the table is honest in general. The commercial question is whether a claim is important enough to influence your decision and, if so, what evidence would make it more reliable.

Good scepticism sounds like due diligence

Suppose a supplier asks for a price increase and says a major raw-material input has risen 14 percent.

Calling the supplier dishonest is unlikely to improve the meeting. Accepting the number because it sounds precise is no better.

The useful response is ordinary procurement work. Which raw material? Which index? What reference period? What share of the total cost does it represent? Did any other cost components move in the opposite direction? Was the previous decrease passed through under the same logic? Does the contract define the relevant index or baseline?

The same approach works with statements that are less numerical.

If a supplier says headquarters will not approve a lower price, ask what range has been authorised and what would be required for an exception. If a salesperson says the remaining capacity will be gone by Friday, explore what allocation decision is actually being made, when it becomes binding and what happens to the buyer's existing requirements. If a counterpart describes something as "company policy", ask for the policy or for an example of how it has been applied in comparable cases.

None of these questions requires an accusation. They simply make important claims carry some evidential weight.

That is a useful habit because weak claims are easy to state once and harder to maintain coherently through several specific follow-up questions.

Body language is a poor substitute for verification

Deception creates an understandable desire for shortcuts. Negotiation training has often promised that hesitation, gaze, posture or vocal changes can reveal when someone is lying.

That is a dangerous level of confidence. Nervousness can come from pressure, status, language, personality or the importance of the meeting. A confident executive can deliver a misleading statement without displaying any obvious cue. Treating behaviour as proof risks accusing truthful people and trusting practiced ones.

Procurement has a better tool available: test the substance.

A cost claim can be reconciled. A deadline can be explored. A capacity statement can be tied to operational consequences. An approval limit can be probed for process. Some claims will remain unverifiable, and that itself should affect how much weight the buyer gives them.

The discipline is to avoid turning an assertion into an internal fact simply because it was delivered confidently.

Your own credibility has a commercial value

There is also a reason to keep a stricter standard for your own statements than "could I get away with this?"

Supplier relationships continue after the negotiation. Claims made at the table can reappear in an email chain, an implementation dispute, an executive escalation or a later tender. A fabricated fact may win a small movement today and make every future statement more expensive to believe.

A buyer does not need to disclose their complete position. They can keep alternatives private, decline to reveal limits and frame information strategically. The cleaner line is to avoid inventing facts that others may rely on.

A simple internal test is useful: would we still be comfortable defending this statement if it appeared later in a written record reviewed by our management, legal team or the supplier?

That is a more durable standard than trying to guess where the boundary of acceptable bluffing sits in every individual negotiation.

The skill worth practising is what happens after the claim

The difficult moments are usually not obvious lies. They are plausible assertions delivered when there is little time to investigate them.

"The capacity disappears Friday."

"Our board has set a hard floor."

"Every customer is accepting the increase."

"This clause has never been changed for anyone."

A buyer needs a repertoire for the ten seconds after one of those statements lands. Ask for evidence? Explore consequences? Test consistency? Note it and continue? Challenge the relevance rather than the truth? The right move depends on what the claim would change commercially.

That is a more useful training objective than teaching people to spot liars.

Voice2Evolve simulations can put these claims into a live negotiation and force the buyer to decide what deserves scrutiny. The review afterwards can look at whether a material assertion was tested, accepted without evidence, challenged too aggressively or converted into a useful line of inquiry.

The 2026 research is valuable because it treats deception in negotiation as something professionals encounter and interpret differently, rather than as a classroom puzzle with one obvious boundary. Procurement does not need to become cynical in response. It needs to become precise.

Keep private what you are entitled to keep private. Be careful with factual claims of your own. And when the other side says something that could materially change the deal, test the claim rather than trying to read the person.

Sources

• Jung, S., Gélvez Álvarez, L. M., & Krebs, P. (2026). Does Professional Practice Shape Judgment and Expectations about Lies in Contract Negotiations? Negotiation and Conflict Management Research, 19(3), 129–157. Journal listing
• Freie Universität Berlin, Empirical Legal Studies Center. Research seminar summary
• Jung, S., Krebs, P., & Leszczynska, M. (2026). Does It Matter What People Lie About?, European Journal of Empirical Legal Studies.