Player > Feats > Sense Assumptions
You can easily intuit a person’s preconceptions.
Sense Motive 1 rank.
You gain a +1 insight bonus to Sense Motive checks. In addition, you can attempt a Sense Motive check to discern some of another person’s assumptions after 1 minute of conversation, allowing you to assess the difficulty of lying to them. The DC of this check is equal to 10 + the target’s Bluff skill bonus or 15 + 1-1/2 × the target’s CR, whichever is higher. If you succeed, you learn whether you would take a penalty to Bluff checks when attempting to convince that target of one falsehood of your choice related to the topic of conversation. If you fail by 4 or less, you learn nothing. If you fail by 5 or more, the target realizes you are trying to glean information from them. You can retry this check, but the DC increases by 5 for each previous failure on this check against that target.