Funnily enough, I notice confirmation bias quite a bit in a D&D game I am currently DM of. I'm playing with a group of friends who are big into video games, and as a result they consistently seek resolutions to conflicts in D&D by way of what they know from shooters: kill everything in sight. Yes, it's at times a valid answer, but it's not the only one and it's certainly not the most interesting one. The best way that I've seen the confirmation bias dissipate from their thinking is to put them into situations where their bias just doesn't help at all.