Scientists have found that the way people vote can depend on much more than the issues being debated.

Nick Chater, Professor of Behavioural Science, revealed through a series of experiments how easily people’s voting intentions can be influenced.

As the UK General Election draws closer political parties of all colours are bombarding voters with pledges, information and speeches, but on BBC Radio 4’s The Human Zoo Professor Chater argues subtle psychological effects could be just as effective.

Professor Chater said: “Many of our decisions are surprisingly dependent on the context; they are very momentary and are actually quite easy to push around and even change.

“We have a jumble of different thoughts in our minds and that jumble gets resolved when we are asked a question - such as which way you’d like to vote; but at another moment, in a slightly different context, our thoughts may get resolved in a different way. We are largely unaware of the capricious factors that drive our decisions.”

Professor Chater reveals several psychological devices that will influence which way people will vote on May 7.

The first persuades people to argue against their own beliefs. A quick survey of members of the public asked if spending on the NHS should be ring-fenced. Without them knowing their answers were reversed; but instead of pointing out the mistake when the survey was discussed, many argued for the point of view they think they just gave - the opposite view from what they actually chose.

“This is known as ‘choice blindness’,” said Professor Chater. “On many issues people are quite conflicted, so it is easy to push them around. In our small experiment, one person was for ring-fencing the NHS, but when we reversed his answer, he accepted that this must be what he had said and started arguing against ring-fencing. This has been repeated many times in experiments and often people are very happy to defend an opinion they didn’t give before. When you explain what has happened to them people are bewildered.

“In one experiment on choice blindness people were asked for their voting intentions before and after their answers were changed. They found their voting intentions changed after their argument had been shifted. A lot more people are open to change than is thought, much larger than the usual 10-15 per cent of swing voters that is often quoted in the media.”

Professor Chater also revealed that candidates' faces can be a powerful influence on voting.

“People were shown photos of the winners and runners-up in a US election,” said Professor Chater. “They were asked between the two who was the most competent. People agreed on the image judged to be most competent and that was mostly the winner in the election.

“It shows how quickly people make a judgement and it is understandable, because during an election campaign we are bombarded with so much information, our brains can’t possibly process it all. Instead we take shortcuts and judging competency by appearance is an understandable shortcut.”

A lot of facts and stats are thrown about during a campaign, but scientists have found they have surprisingly little effect on voters.

People were asked if crime is on the increase. Some felt it was and even when shown a graph from the British Crime Survey showing it has been in decline for the last 20 years, some would not change their mind. Resistance to facts can be quite extreme.

“Scientists infiltrated a cult that thought the world would end, but of course when it didn’t instead of changing their belief, the members thought their actions had saved the world, and so they stepped up their efforts to recruit more members to the cult,” said Professor Chater. “Even then facts don’t change people’s minds. It seems when we are in a social environment where we have each other as support for our actions and attitudes facts make little impact.”

Another experiment showed how easily “primed” people can be in their political thinking. Leaving a dead plant in a room and turning the heating up made people more likely to feel that global warming was an important issue.

“We are more influenced by our own personal experiences and anecdotes than by data,” said Professor Chater. “One study found in the US that the US flag, after 9/11, had become a strong Republican cue, and when the flag was presented on a survey more people said they would vote Republican. Experiments have even found that putting the voting booth in a church as opposed to a school effects the way people vote.

“These experiments show how easily our decision on who to vote for is pushed around, much more than we realise.”

Listen to The Human Zoo election special here.

Visit The Human Zoo weblab to take part in its online experiments.

Professor Nick Chater teaches Behavioural Sciences for the Manager on the Warwick Executive MBA and Principles of Cognition on the suite of MSc Business courses. He also teaches Emotions in Business on Warwick Business School's Undergraduate courses.