How did ancient Asian interrogators use dry rice to judge suspects?

In ancient Asia, interrogators utilized a method based on the physiological principle that nervous tension causes a decrease in salivation.1

To judge a suspect, authorities would fill the mouths of several individuals with dry rice. Because the stress of lying inhibits the production of saliva, the suspect who experienced the greatest difficulty in spitting out the rice—due to their mouth remaining dry—was judged to be guilty. This practice represents an early attempt at lie detection by observing involuntary physical responses to psychological pressure.1