Is there a single word to describe someone who often attributes inappropriately trivial/cheap motives to another person's actions? I'm thinking along the lines of someone who puts himself briefly in that position and usually assumes the easiest/least flattering motive for other people's behavior. I know "cynical" might be of use here, but I'm wondering if there's a narrower/more specific word to describe this?
For example: Person A and person B both take a test that can be passed or failed. Person A calls person B on the phone in hope of getting the test results only person B (for an irrelevant reason) has access to. Before person B discloses the results, person A asks if the situation is bad, referring to whether they both failed. Person B claims the situation is worse, as a matter of fact, person A failed and person B passed the test (clearly assuming person A will see the situation in the same way). Person A actually thinks this is an objectively better situation and puts person B's success over the comfort of not being worse than them.