The validation model of causal bridging inferences proposed by Singer and colleagues (e.g., Singer in "Can J Exp Psychol," 47(2):340-359, 1993) claims that before a causal bridging inference is accepted, it must be validated by existing knowledge. For example, to understand "Dorothy took the aspirins. Her pain went away," one first computes a mediating idea RELIEVE [ASPIRIN, PAIN]. Then, the truth of it is validated on the basis of existing knowledge. The present study examined the hypothesis that a causal inference would be drawn and validated even when validating knowledge is not familiar or available because elaborations are made to retrieve or construct such knowledge. Experiment 1 showed that people tend to judge naturalness of a text based on causal relations and that causality was indeed recognized in those texts in which the antecedent sentence and the consequence sentence are not linked by familiar knowledge. Experiment 2, which measured sentence reading times, showed that while sentence processing times were longer for such texts than texts involving familiar knowledge, there was no difference between these texts in reading the subsequent sentence describing the validating idea. These results provided evidence supporting elaboration as well as validation of causal bridging inferences.