This is one big challenge on the field, irrespective of the user segment or geography you are dealing with, and culture adds a lot of complexity. While on the field, I am extremely attentive to the conversation, their body language, and the environment to be able to catch this in the moment and probe deeper. As you have mentioned, learning about their past, environment, relationships etc. can throw some light on this and prevent you from getting trapped in their ‘fake stories’.