In 1938, psychologist Gregory Razran found that his subjects developed a more favorable view of the people and things they experienced while they were eating – a result Razran coined as the “luncheon technique.”

So the next time you have an important negotiation, consider having lunch or dinner with your counterpart first. And consider picking up the tab to engage the reciprocity rule, which psychology professor Robert Cialdini describes as the human tendency to want “to repay, in kind, what another person has provided to us.” In other words, to return the favor – perhaps as soon as in the subsequent negotiation.