Have you ever noticed…

What is confirmation bias?

This question comes via Cantras from Twitter.

“Confirmation bias” is a concept from psychology which refers to the way people tend to look only for the information that confirms what they already believe. This can encourage belief in conspiracy theories and the supernatural, even where evidence exists disproving them. For example, I’ve noticed that my rabbits will often startle before the doorbell actually rings. This would imply some sort of sixth sense, if it were true, because we live up one storey and not near the actual front door. However, if I treated this as a scientific experiment and recorded how my rabbits react every time the doorbell rings, I would probably find that for a significant portion of the time, they don’t actually startle before the doorbell rings.

Not actually one of my rabbits, but it sure looks attentive.

In other words, the fact that they’ve startled just before the doorbell rings on some occasions is down to pure chance. It doesn’t seem that way to me, because I noticed it apparently happening once, and then searched my memory for other occasions when it did happen — not for occasions when it did not happen! Our brains automatically give more weight to events we think are significant.

Confirmation bias can be a problem for scientists as much as anyone else. If you have a great theory, you want it to be true. That’s why scientists have to be very careful in setting up their experiments and recording data: if they only take note of the times when their experiments work, for example, they could be seeing an effect which is actually just down to luck.

It’s a natural way for our brains to work: it’s useful to find patterns in the world around us. If you always hear a particular noise just before a predator attacks, it’s prudent to react to the noise. It’s possible that in reality that noise isn’t made by the predator, but if the two are linked often enough, noticing that linkage can save your life out on the savannah. In other words, noticing that pattern is “adaptive”, and people or animals who can do that are more likely to survive and reproduce.

However, it becomes a problem for us in society because it’s not just about survival. It can cause us to subscribe to harmful stereotypes, and can even allow people to hijack our minds to spread prejudice, despite our best intentions. We can fight back against that individually, though, by always trying to think of when a given statement wasn’t true. If someone tells you “all eggs are brown”, you might think back to the eggs you buy in the shop and agree — but if you take a moment to think about it, you’ll probably remember seeing eggs with different coloured shells.

One thought on “Have you ever noticed…

  1. Related phenomena: Cherry picking, cognitive bias. You could cover them, if you liked. Ooh! More distantly related: correlation vs causation and false correlations. That’d be a good topic, too.


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