As Scotland prepares to decide its future in the independence referendum, how will voters make up their minds? BBC Scotland's Science Correspondent Kenneth Macdonald asks whether the head or the heart will prove decisive.
Political scientists are increasingly adapting techniques from psychology and neurology to understand how we make political decisions.
Their findings suggest that our rational thought processes do play a part - but that our hearts are in the driving seat.
The science of campaigning will be examined on Tuesday in a BBC Scotland documentary.
It's a big decision, potentially the biggest political choice, you'll ever make.
You'll carefully examine the arguments for Yes and No, painstakingly assessing the issues, then arrive at your rational decision to vote one way or the other.
Or will you?
Could it be that when it comes to making political choices our hearts rule our heads? Or, more precisely, the emotional parts of our brains take precedence over our rational faculties?
Dr Rob Johns thinks so. He's a political scientist from the University of Essex who's using psychological techniques to uncover how we really make our democratic decisions.
As the people of Scotland weigh up how to vote in the independence referendum, they are asking questions on a range of topics from the economy to welfare.
In a series running up to polling day, BBC correspondents are looking at those major questions and by using statistics, analysis and expert views shining a light on some of the possible answers.
His findings suggest that while we're influenced by both head and heart, it's our hearts that win out:
He says: "We are as human beings programmed - or hard wired as they put it - to react to our emotions.
"And one of the reasons for that is that rational calculation is immensely arduous.
"Anybody who sat down and tried to work out the pros and cons of independence would need an Excel spreadsheet, a lot of time and a great deal of patience.
"Some people might fondly imagine they're rational calculators. They're kidding themselves."
Strictly speaking this is not really head vs heart, more the emotional circuits of our brain trumping the rational ones.
The slightly disturbing conclusion - disturbing, that is, for those of us who like to think they weigh up conflicting arguments with dispassionate, Spock-like logic - is that baser instincts are at play.
To examine the emotional underpinning of our political choices Dr Johns and I waylaid a self-selecting sample of BBC staff.
We were equipped with a ballot box and two photographs: one of a woman with a tarantula on her face, the other of a particularly nasty-looking verruca.
There were two questions on the ballot paper: Yes or No to independence, and a request to rate just how disgusting those photos were.
Given that our unsuspecting subjects had been waylaid on the way to lunch, this wasn't going to find its way into a peer reviewed journal. But the results were nonetheless intriguing.
BBC Scotland has been broadcasting a series of in-depth films looking at various aspects of the Scottish independence referendum debate.
- Journalist Allan Little headed overseas to look at whether Scotland could take inspiration from the Nordic economic model.
- Newspaper columnist Janet Street-Porter walked the length and breadth of Scotland speaking to people about the referendum.
- And Reporting Scotland presenter Jackie Bird asked the question: "What do women want from the referendum debate?" Look up many more on the BBC iplayer and look out for others to come.
Dr John explained he was testing the increasingly accepted hypothesis that the way we react to physical fear and threat manifest themselves in our political views.
"Broadly speaking, conservatives - small 'c' conservatives - are more prone to fear," he said.
"You find that those whose skin crawls more when confronted with threatening images like these are also more likely to have small 'c' conservative opinions.
"We're kind of pioneering the test of whether that conservatism extends to sticking with the status quo constitutionally."
And that's what happened. When we turned out our ballot box, the papers showed those who found the pictures extra-yucky (admittedly that's not a scientific term) were more likely to have voted No.
Yes voters, on the whole, were less easily shocked by the spider-verruca images.
In campaign that's been characterised as hope vs fear, that could have implications for both sides.
Other political scientists are looking even deeper, not just into our minds but our brains.
At Edinburgh University Professor Laura Cram is using a functional magnetic resonance imaging (fMRI) scanner to examine which parts of people's brains become active when faced with political choices.
In one experiment she's asking her Scottish subjects to empathise with videos of people with shoulder pain. Can they rate how much pain they're in?
What they don't know is that they've also been shown random, subliminal images. Sometimes they're blank, sometimes a Saltire; sometimes a St George's Cross.
Will the flags affect their judgment? We'll have to wait until her final paper is published. But researchers in the US have been using similar methods for more than a decade.
At Emory University in Atlanta, Professor Drew Westen put subjects in an fMRI machine during the 2004 presidential race between George W Bush and John Kerry.
For Republicans and Democrats the task was the same: watch your preferred candidate contradicting himself, then try to explain what had been said.
Professor Westen watched as the political partisans' brains reacted. Would reason or emotion rule?
"We found no reasoning going on at all," he says.
"Kerry supporters all found Kerry's remarks completely consistent and non-problematic.
"Bush supporters found all his remarks completely non-problematic.
"And it wasn't until about 20 seconds later that we started to see the activation of reasoning circuits.
"What we hypothesised was going on was people were starting to rationalise the conclusions that they wanted to come to."
Research on political partisanship in America might not seem relevant to undecided voters in Scotland.
But it underlines the idea that while some of us may think we don't know how we'll vote yet, our hearts - if not our minds - are already made up.
All this comes with the customary caveats. All science is provisional, and much of this science is in its infancy.
FMRI scans can only reveal blood flow in the brain, not how billions of neurons are functioning. Our minds are massively complex structures.
Each of us is unique. And whether it's your heart or head that ultimately decides, it'll be your decision - and yours alone.
Mind Games, one of a series of BBC documentaries on issues surrounding the referendum, will be shown on BBC Two Scotland at 21:00 on Tuesday and will be available afterwards on the BBC iPlayer