Self-reporting can be a fine measure. For example, these participants who were amused by people they disagree with being beaten up self-reported low empathy.

Self-reporting can be a fine measure. For example, these participants who were amused by people they disagree with being beaten up self-reported low empathy. They just didn't know that's what they were doing, which is why they were honest about it. You can measure things better that are unpopular. On a U.S. college campus, you can measure lack of empathy but not empathy, whereas in ancient Sparta you could measure empathy but not lack of empathy.