Source | mindhacks.com| tomstafford
How do you persuade somebody of the facts? Asking them to be fair, impartial and unbiased is not enough. To explain why, psychologist Tom Stafford analyses a classic scientific study.
One of the tricks our mind plays is to highlight evidence which confirms what we already believe. If we hear gossip about a rival we tend to think “I knew he was a nasty piece of work”; if we hear the same about our best friend we’re more likely to say “that’s just a rumour”. If you don’t trust the government then a change of policy is evidence of their weakness; if you do trust them the same change of policy can be evidence of their inherent reasonableness.
Once you learn about this mental habit – called confirmation bias – you start seeing it everywhere.
This matters when we want to make better decisions. Confirmation bias is OK as long as we’re right, but all too often we’re wrong, and we only pay attention to the deciding evidence when it’s too late.
How we should to protect our decisions from confirmation bias depends on why, psychologically, confirmation bias happens. There are, broadly, two possible accounts and a classic experiment from researchers at Princeton University pits the two against each other, revealing in the process a method for overcoming bias.
The first theory of confirmation bias is the most common. It’s the one you can detect in expressions like “You just believe what you want to believe”, or “He would say that, wouldn’t he?” or when the someone is accused of seeing things a particular way because of who they are, what their job is or which friends they have. Let’s call this the motivational theory of confirmation bias. It has a clear prescription for correcting the bias: change people’s motivations and they’ll stop being biased.
The alternative theory of confirmation bias is more subtle. The bias doesn’t exist because we only believe what we want to believe, but instead because we fail to ask the correct questions about new information and our own beliefs. This is a less neat theory, because there could be one hundred reasons why we reason incorrectly – everything from limitations of memory to inherent faults of logic. One possibility is that we simply have a blindspot in our imagination for the ways the world could be different from how we first assume it is. Under this account the way to correct confirmation bias is to give people a strategy to adjust their thinking. We assume people are already motivated to find out the truth,
they just need a better method. Let’s call this the cognition theory of confirmation bias.
Thirty years ago, Charles Lord and colleagues published a classic experiment which pitted these two methods against each other. Their study used a persuasion experiment which previously had shown a kind of confirmation bias they called ‘biased assimilation’. Here, participants