Decision trees as a model of chance perception

The results of interviews to refugees of South-Hyogo earthquake (1995) show that the human process into the awareness of rare hazards is composed of context-shifting of people. Supported by studies in cognitive science relevant to risk management, this paper models context-shifting by means of decision trees, with nodes describing human-concerned contexts and situations. The optimal explanation, i.e., the most useful statement for navigating people to the understanding of the meaning of a certain event or situation, is formalized as the shortest path on the set of decision trees connected by loose bridges, from his/her initial concern to the understanding of the situation/event in question. This framework is devoted especially to aiding people in dealing with rarely significant situations, i.e., fatal risks or beneficial opportunities, which we call chances here.