Confirmation bias, put plainly, is seeking out evidence that confirms your opinion or belief is correct while ignoring or undervaluing evidence to the contrary. No one is immune to this tendency for a very obvious reason, we all prefer to be right!
Without making a proactive effort to avoid this potential pitfall, it can sneak into our areas of interest, especially those we're most passionate about. Think politics, an argument with a loved one, or a friendly debate over who's the best baseball player of all time.
While these can all lead to hurt feelings, or even the unthinkable, sounding foolish... When it comes to investing, it's just downright costly.
Here's a quick read with some tips to give your ideas and convictions the fair shake they need before diving in.