The reason a friendly tone can raise the price

Twenty minutes of easy conversation about a shared city, then the figure arrives. It is higher than expected, and the counter that would have been automatic in a cold exchange now feels like an odd thing to do to somebody who has just been pleasant.

What everyone sees

Rapport is treated as separate from the substance — a lubricant that makes the process pleasant while the numbers are settled on their merits. Rapport is not separate. It changes what each side is willing to say next, and the first number said under those conditions is more likely to survive.

What is actually happening

Drolet and Morris found that face-to-face rapport increased cooperative behaviour and improved joint outcomes, so the effect is real and often mutually beneficial rather than manipulative. Galinsky and Mussweiler supply the countervailing half: first offers exert a strong anchoring effect on final agreements, with the anchor’s power reduced when the recipient actively focuses on their own alternatives or on the opponent’s reservation point. Warmth interferes with exactly that defence, since the socially natural response to a pleasant counterpart is accommodation rather than a deliberate search for reasons the number is wrong. The result is not that friendliness is a trick. It is that friendliness raises the survival rate of whichever number is spoken first.

Why it stays hidden

The effect hides because both parties like the interaction and both report it as productive. Nobody records the counter-offer they did not make, and there is no moment where accommodation is chosen — the aggressive response simply never becomes salient enough to select. A pleasant negotiation is remembered as a fair one.