I’ll tell you what I’m going to do. I’m going to try to understand why certain Scottish voters, including me, behave the way they do. I’m also going to try to understand why, when politicians go on public forums, there’s so much nastiness and abuse. The Scottish Tory leader Douglas Ross did a Facebook Live event the other day and a fair proportion of the comments scrolling up the screen were abusive and aggressive. Why?

Part of the explanation is Facebook itself, which seems to circumvent many of the conventions we usually work to; it really is remarkable how quickly conversations on the site, and others like it, turn nasty. To be fair, there’s also going to be a fair proportion of the audience who just think Mr Ross is rubbish, or wrong, and they’re going to get wound up. Tories have always had the ability to get blood boiling in many Scottish veins, and that’s fair enough. People get angry.

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The ridiculing and abuse of politicians, even the greatest, is also nothing new. I’ve been reading Bob Holman’s brilliant short biography of Keir Hardie recently, and it describes some of the abuse the Labour leader suffered, even from his own side. When Hardie showed up at Parliament in a plain suit and cap, the trade unionist TR Threllfall said he had “outraged the sentiment of Labour” and the “first assembly of gentlemen”. Hardie was also shouted down and abused by supporters of the First World War, and even Churchill wasn’t beyond abuse: it’s said that he was booed during a visit to the bombed-out East End during the Second World War.

But I think it would be fair to say, now that ridicule comes via a phone rather than a placard, that politicians in Scotland face abuse with an extra element added by the outlook certain voters have on the constitution. Someone called Calum, for example, asked Douglas Ross if he would promise to leave Scotland “when we get independence”. Another one called William told Mr Ross “you’re not wanted in Scotland”. Mr Ross says he intends to continue with the Facebook events despite the abuse, but it was obvious that this type of comment in particular gets on his nerves.

Here’s what the Tory leader said in reply to Calum: “So you’re saying someone who’s Scottish, born and bred, and raising my own family here, has to leave this country if you were ever to get your way in having independence. That’s your message to the people of Scotland? If you disagree with us, leave this country? Well, Calum, if that’s your argument, shame on you.”

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And here’s what he said to William: “This is my country as well as yours. Don’t think just because you support independence and I support Scotland’s strong place in the UK that this is therefore not my country. I think you’ve really got to look at what that message sends out to people – people who are unsure about separation, they may support it, or they may stay as part of the UK. Do you think you’re winning many arguments by telling people that it’s not their country anymore if you become an independent Scotland? That’s not a message that any politician of any party would endorse in any way.”

I think most of us, away from the cauldron of Facebook, would agree with Mr Ross: no-one should have to leave Scotland, or feel they don’t belong in the country because of their opinions on the constitution. But, having said that, it’s not uncommon to see comments along those lines (I get them myself every week): “you’re not Scottish”, “get out of Scotland” and so on. Who’s making them? And where are they coming from?

There’s a couple of parts to the answer, I think. First, nationalists are prone to seeing party, country, and self as one and the same thing. Not only that, the sense of national identity – and this particularly applies to Scotland – often comes from our personal or historical impressions of hurts or wounds inflicted by another group (in our case, the English, or those seen to be co-operating with the English). It’s why people get angry and it’s probably why nations are one of the few things that some people are willing to die, and kill, for.

But it goes even deeper than that. As well as Bob Holman’s Keir Hardie biography, I’ve been reading Melanie Challenger’s new book How to Be Animal, published next month, and it has some interesting and relevant things to say about politics. Challenger has delved into why humans behave the way they do and one of her subjects is why we tend to divide into groups and then start defining each other by membership – or non-membership – of those groups.

Her answer is simple: it’s natural. Humans originally split into groups, which can become nations, to improve our survival chances, and the emotions it fosters still linger in our animal brains. But Challenger goes further: the research, based on scans of brain activity, shows that “inside a coalition, we come to see our worldview as richer in its inherent intelligence, but we can also see those with other worldviews as having less mind than we possess.” In particular, Challenger highlights studies by the psychologist Jonathan Levy on young Israelis and Palestinians: both sides, he says, shut down the brain’s automatic responses to the pain of those on the other side.

I think, more or less, this is what’s going on with Mr Ross’s most aggressive critics. First, they see their coalition (as defined by nation and party) as better than others, which leads to them dismissing or abusing anyone who is not a member of the coalition. As I’ve said, it’s something we all do to some extent, but nationality is a particularly powerful coalition which is why the reactions are also so powerful. William, Calum, and others think Mr Ross should “leave Scotland” and Mr Ross is irritated by that. I know how he feels. Attachment to a coalition, and antipathy to anyone who doesn’t belong to it, lies deep in our animal brains. Our responsibility as humans is to resist it.

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