Petrov later indicated that the influences on his decision included that he had been told a US strike would be all-out, so five missiles seemed an illogical start;[1] that the launch detection system was new and, in his view, not yet wholly trustworthy; that the message passed through 30 layers of verification too quickly;[11] and that ground radar failed to pick up corroborative evidence, even after minutes of delay.[12] However, in a 2013 interview, Petrov said at the time he was never sure that the alarm was erroneous. He felt that his civilian training helped him make the right decision. He said that his colleagues were all professional soldiers with purely military training and, following instructions, would have reported a missile launch if they had been on his shift

Just a sensible person.