Can you trust flipped politicians?

John Key manipulated by the "Thatcher effect".

How trustworthy and likable are New Zealand's leaders and politicians once they've been Thatchered?

Upside-down photographs of some of New Zealand's leading politicians may hold the key to why voters trust them or not.

A University of Canterbury marketing study has applied the so-called Thatcher Effect on images of Prime Minister John Key, Labour leader David Cunliffe and former Justice Minister Judith Collins to look at perceptions of trustworthiness in the run-up to the election.

Labour leader David Cunliffe "flipped".

The Thatcher Effect was first illustrated in the 1980s using images of former British Prime Minister Margaret Thatcher, which flipped her face vertically, except her smile and eyes.

Researchers showed that when a person's face was flipped upside down, with the smile and eyes left in the original position, people can still identify the image.

University of Canterbury marketing associate professor Ekant Veer has used that idea to lead a study looking at perceptions of trustworthiness and likeability that are linked to perceptions of beauty in campaign photos of different politicians.

"I used the Thatcher Effect as a way of seeing how implicitly people were able to see a normal image. Those people who felt the flipped image was quite normal also showed high levels of trustworthiness towards the person," Dr Veer said. "While those who found the images quite affronting had the opposite effect."

Judith Collins "flipped".

Almost 1000 New Zealanders were surveyed in the study, which used images of Mr Key, Mr Cunliffe and Ms Collins with their smile flipped, and 250 North Americans as a control group.

"Five hundred participants were shown the Thatchered images and were asked to rate their perceptions of beauty when the image was flipped, all except the smile. We showed the opposite images to 500 more New Zealanders and conducted the same study," Dr Veer explained.

"We then linked the difference between these two groups to perceptions of trustworthiness from 250 North Americans who reported to know nothing about New Zealand politics, so as not to impact any political affiliation.

"We found that the politicians that showed the lowest difference between the different images also received the highest levels of trustworthiness from the North American audience.

"Those with the greatest beauty difference reported significantly lower levels of trustworthiness. For example, Judith Collins had the highest disparity between her two images and also the lowest levels of trustworthiness."

The research could have implications for how some people could implicitly make associations between the trustworthiness of a politician and their campaign material, Dr Veer said.

"When a large Thatcher Effect is shown to exist, perhaps a smile is not the best thing to be plastered over campaign material, and it could be a good reason why John Key's smiling image on every National billboard is helping in the lead up to the election," he said.

"It could also offer evidence as to why John Key is able to maintain significantly higher levels of public support as preferred Prime Minister despite the Nicky Hager book, while David Cunliffe's mistakes with capital gains tax only further solidifies implicit perceptions of less trustworthiness."