How do we make our political choices? We stand in the polling booth weighing up the different policies of the various parties and then select according to taste, don’t we? Like picking clothes off a rack. Ooh, I need something medium in red, I’ll take Stella Creasy, that sort of thing. Or, perhaps more accurately: I believe in gender equality and the redistribution of wealth, Labour agrees with me on those issues, so I’ll vote Labour.

We might think that’s how it works. But this sort of sifting is only part of the story. We also – and to a greater extent – shift our political views to align with our political parties, and – importantly – to also distinguish ourselves from our political opponents.

During the 2016 presidential election, American voters were more divided than ever on questions of race and gender. But, as Matt Grossmann points out in a piece for the politics-stats-nerd site FiveThirtyEight, research using ‘panel studies‘ found that, for instance, white Democratic voters became took harder stances on race and sex discrimination in response to Donald Trump’s inflammatory comments on those topics, rather than already having those stances and then being appropriately appalled by the comments.

Are you in control of your politics? By Peter Franklin

It’s not only political parties that have this effect. We also align ourselves with more loosely defined tribes, such as Leave and Remain, or centrist, or conservative, or socialist – and we change our views to match our alignment.

We already know this, though. We know that our views are a product of more than just reasoned reflection. We know that even though we feel like our logical brains are in charge, they’re not. In the words of Jonathan Haidt, they are more like a press secretary than a president, justifying our emotional decisions in rational language. And part of our emotional response is socially mediated: say, my in-group is Democrat voters (or Labour voters, or Remain voters), so I want to signal that I share views with them. My out-group is Trump/Tory/Leave, so I want to signal that I have very different views to them. So I plant my flag deeper into the territory to remove any ambiguity.

But that knowledge doesn’t make it any less unsettling. I don’t like the idea that my views on, say, the #MeToo movement or trans rights or Black Lives Matter are not fully my own. Worse, it undermines my confidence in my own opinions. If I know I’ll probably change my political opinions – have already changed my opinions – because of a subconscious need to fit in with my in-group, then I might not be so certain that I went for the right ones in the first place.

Are you in control of your politics? By Ben Cobley

It’s not just the big moral questions we shift on, but also specific policies. Rob Ford, a political scientist at Manchester who I spoke to while writing this piece, points to a situation in Denmark. Helle Thorning-Schmidt, the then prime minister, changed her mind on an issue to do with the state pension. (It doesn’t really matter what the issue was.) At first, voters for her Social Democrat party were against it, as she was. But when Thorning-Schmidt changed her mind, so too did a large percentage of SD voters: their views changed to match the party.

You will want to say: “But I arrived at my views through reasoned reflection! I hold my views on the gender pay gap and what to do about it not because of my political tribe, but because they are the right ones.” But you don’t. They may or may not be the right ones, but you arrived at them, partly, through tribal effects.

It’s like vision: we think we’re getting a true, unmediated view of the world through our eyes. But actually we’re constantly filling in the picture in from our expectations – something that certain optical illusions reveal.

Similarly, you can see via experiment how tribal allegiances affect our beliefs. Ford gave me a simple example: he asks new undergraduates to rate two speeches, one by Barack Obama and one by George W Bush. The undergrads, unsurprisingly, always prefer the Obama one.

He then reveals that, in a mean little trick, he’d actually switched them around. The one they thought was Bush was Obama and vice versa. The students are, consistently, “shocked and upset” to find that their opinions of the speech are driven by their political opinions of the speaker rather than the content of the speech itself.

Are you in control of your politics? By Matt Goodwin

It’s also worth noting that when we change our mind, we don’t remember doing so. We believe we always believed what we believe now. For example, a majority (54%) of British people supported the Iraq war at the time – but when they were polled in 2015, only 37% of people said they had backed it. In the US those figures were 63% and 38%. Millions of people changed their minds without noticing, and backdated it so that in their memory they always believed it. These tribal effects happen insidiously: when our tribe changes its view, we change with it, and we forget that we ever thought differently.

We also change our views to distinguish ourselves from our opponents’ tribes. There really is a ‘backlash’. This gets satirised as “fascists only become fascist because we called them fascist”, but while that stupid caricature is obviously false, it is absolutely true that people become more entrenched and extreme when their political opponents do.

So the thing that really made Americans get on board with Obamacare was Donald Trump trying to repeal it. Democrats took ever-more liberal stances on race because they were defining themselves against Trump. Remainers in Britain started waving EU flags around and caring very deeply about the Customs Union in part to distinguish themselves from Leavers (and vice versa).

Again, you can see this in specific examples. New Zealanders voted in two referendums in 2015 and 2016 on whether to change their flag. The centre-Right National Party leader, John Key, came out in favour. A study out last week found that, just as with Thorning-Schmidt, National Party supporters changed their views to match their party – but many centre-Left Labour voters who previously supported the change shifted to oppose it.

Are you in control of your politics? By Frank Buckley

This “negative partisanship”, defining yourself in opposition to a party or group, is a real thing, and Right-wingers absolutely will change their views to become less like the Democrats or Labour. And, yes, that means their views will become less liberal on issues of race and sex – “more racist and sexist”, if you prefer – as a response to movements in the other direction from the other side.

You can, if you’re on the Left/progressive/liberal side of the argument, shrug that off and say “Well if it only took me calling Right-wingers racist to make them racist, I guess they were always racist”. But we live in polarising societies. We push ourselves further to the extremes in response to our opponents doing the same. If I’m trying to get my views as far away from Brexiteers’ views as I can, and Brexiteers are doing the same to me, then we’re going to end up a long way away from each other.

And, sure, you might want to be a long way away from your opponents, because they’re bad and terrible people. And, true, it’s not that the virtuous position is halfway between “Nazi” and “non-Nazi”; there really are some things which are morally wrong and which we ought to distance ourselves from.

Are you in control of your politics? By Douglas Murray

But you, good and virtuous person that you are, do not believe what you believe solely because you have weighed the pros and cons and risks and benefits and arrived at the moral truth. Nor have I. We have done so, partly, to signal membership of one tribe and opposition to another. And by doing it we push others to do the same. Angrily denouncing “communist” Corbynites or “racist” Brexiteers will push those people further into their camps, making them more of the thing we purport to dislike. The end result is two wooden palisades marked “liberal” and “conservative”, each filled with people sure of their own righteousness and the enemy’s evil, staring at each other uneasily through rifle sights.