Thirteen types of behavior, such as guests touching plates, guests shaking hands with others and waiters serving dishes, were assumed for both guests and waiters, and these assumed surface touching behaviors and their frequencies are summarized in Table S4. Because the six parties were discrete , it was assumed that guests did not shake hands with those at different tables. Seven types of pathways were considered regarding the behaviors of the waiters when serving dishes and wine. As shown in Figure 2A and Figure S1A, the waiters served guests at one table after another in anticlockwise and clockwise directions in Pathways 1 and 2, respectively. As shown in Figure 2C and Figure S1C, the waiters served guests at half of a table after another half in anticlockwise and clockwise directions in Pathways 3 and 4, respectively. As shown in Figure 2E and Figure S1E, the guests were divided into three groups of roughly equal size (Tables 1 and 2 and half of Table 3, the other half of Table 3 and Tables 4–6), and for every serving, each waiter served one group of guests in anticlockwise and clockwise directions in Pathways 5 and 6, respectively. As shown in Figure 2G, the waiters served guests randomly in Pathway 7.