Human communication is considered as the faithful transmission of information. Therefore, when people are involved in communicational exchanges, they should be sensitive to the success with which information is transmitted, easily detecting when conversation lacks coherence. Faithful information transmission may often conflict with other conversational goals. Additionally, mechanisms supporting information transmission may themselves lead to cases of incoherence being missed. To ascertain the extent to which people are insensitive to conversational incoherence, two experiments in the laboratory repeatedly crossed two unrelated conversations. In the two studies, involving both narrowly and broadly focused conversations, between 27% and 42% of the conversants did not notice that their conversations had been crossed. These findings suggest that it may indeed be unrealistic to model spontaneous conversation as faithful information transmission. The results show that communication involves noisy and error-prone inferential processes, serving multiple independent goals.