Ask HN: Looking for something that was on HN about hidden bias

I remember a long time ago on here reading about a method to identify hidden or subconscious biases. I remember thinking the method was really quite genius in how it worked. It involved something like a list of multiple choice options, and then presenting an additional option for other people in the same list -- hard to remember. But despite all my Googling, I cannot seem to figure out what this was. Does anyone on here know? (Note that this test isn't the Harvard implicit bias website; that's not what I'm looking for.)