Well, that's still the "confronting" test. Given that people answered "because of the other evidence" in various places, either you're wrong about people deciding irrationally, or people are rationalizing a lot (which would make it a non-discriminating test). What sort of test would discriminate between a rational-ish person and someone who originally chose because of some bias ("bias X") and then rationalized, without requiring examination of the annotated bibliography of all the evidence someone ever considered ever?