Logical fallacies – how human brains make a mess of things

Consider this sequence of numbers that follows a very simple rule. All you have to do is figure out the rule: 22, 44, 88.

To help, here’s another sequence of numbers that follows the same rule: 7, 14, 28.

One more: 15, 30, 60.

Have you figured it out yet? Of course you probably have, since it’s plainly quite simple. Just in case, here’s one more sequence: 1, 99, 789.

The bit of your brain that thought the rule involved doubling the previous number (rather than simply any three numbers in ascending order, which was the rule actually being used) was affected by what’s called confirmation bias, which is something all human brains are wired to do. It is a vital part of human thought, but it can cause havoc if left unchecked.

Confirmation bias is the process via which you want to be right about how you see the world, so you seek out information that confirms your beliefs and avoid contradictory evidence and opinions. Simply put: people tend to prefer – or bias towards – things that confirm their existing beliefs and attitudes.

It’s why social media bubbles exist, and why it can be so hard to convince people to change their minds using facts alone; sometimes people actively don’t want to receive information that contradicts their beliefs because people are biased in favour of the beliefs they like. Changing your mind requires more energy than keeping it the same. Research has consistently shown, for example, that presenting anti-vaccination believers with more and better information about the scientifically-proven effects of vaccines does not get them to change their minds (indeed it often serves to strengthen their existing beliefs).

In a family law context, it’s important to be aware of confirmation bias and how it can impact upon a case. A familiar example might be the spouse who for whatever (often entirely valid) reason, has a rather dim view of their ex. Through the lens of their dislike for the other person, that person’s behaviour only serves to demonstrate how much of a wrong ‘un they’re finally separating from. Those missing bank statements, or the reluctance to disclose their tax returns from 7 years ago? That proves they’re hiding something. They want to see the kids for more of the holidays? They’ve always been vindictive and they want to make me suffer by taking my children away. And so on and so on.

Confirmation bias is also important to notice in oneself. I remember at law school being taught the process of the ‘case theory’ when preparing to run a case at trial. What is your case theory? How do you and your client say things unfolded, and how do you present and challenge the evidence to support that case theory? What is the story of your client’s winning case, and how do you tell that story? This is all well and good, but it runs a major risk, if not counterbalanced by other ways of thinking, that you will go through the evidence in a case, find everything that support’s your client’s version, and miss or ignore important evidence to the contrary. If you start with the conclusion firmly in mind, your brain will naturally tend towards finding all the things that support the conclusion, and will diminish or miss altogether the things that don’t.

Trying to avoid confirmation bias at all times is both unrealistic and unnecessary. There are lots of good things that confirmation bias can achieve – it can often be an efficient way of cutting through huge amounts of unnecessary information for example – so it’s not an entirely bad thing. If it were, it’s unlikely to have survived the evolutionary process for this long. Rather, what’s important is to be aware of this tendency in oneself and others, and to adjust and accommodate accordingly.

This is the first in a sequence of shorts looking at fallacies and biases, and how they can be vital to the work we do and the way we live our lives.

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A longer article from The Decision Lab on confirmation bias can be read here.

Today’s recommended video is about the medical test paradox, and is a lesson in double-checking.

Today's recommended track is Paranoid by Black Sabbath.

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