Alternatively or in addition, the message analyzer 232 may determine whether the first communication session and the second communication session share a common ground by determining whether the two communication sessions have a same or similar topic. Even if they do not share one or more keywords, the first communication session and the second communication session may be related to a same or similar topic or subject. If the two communication sessions have a same or similar topic, the message analyzer 232 may determine the first communication session and the second communication session share a common ground. For example, the first communication session may have 10 occurrences of “presidential election,” and the second session may have 8 occurrences of “the White House” and 13 occurrences of “vote.” The message analyzer 232 may determine that the first communication session and the second communication session have a common topic of presidential election and thus may share a common ground.

Alternatively or in addition, the message analyzer 232 may determine whether the first communication session and the second communication session share a common ground by determining whether the two communication sessions are related to a same or similar subject. For example, the message analyzer 232 may determine that the first communication may have 11 occurrences of “planets” and the second communication may have 9 occurrences of “Earth.” The message analyzer 232 may determine that the first communication session and the second communication session are related to a common subject of planets of the Milky Way galaxy and thus may share a common ground.