The inner feelings of people who falsely claim to care about the environment can be exposed by understanding their body language, according to a new book.
Professor Geoff Beattie, from The University of Manchester, says mismatches between gestures and speech will allow us to indentify 'green fakers', regardless of what they actually say.
His research - for the University's Sustainable Consumption Institute - used video recordings to examine the gestures and speech of people with differing views on the environment while they talked about carbon labelling, global warming and their lifestyles.
By examining their gestures, each speaker revealed a fascinating connection between what they were saying and what they actually believed.
In his book, launched this week (June 9), Professor Beattie will urge society's leaders to pursue, understand and change the implicit attitudes which make us buy green products in supermarkets.
At the launch of Why Aren't We Saving The Planet? A Psychologist's Perspective, published by Routledge, Prof Beattie will discuss his work with Tim Harford - the FT's undercover economist and presenter of BBC Radio Four's More or Less, which examines statistical claims made by public figures.
For the book, Professor Beattie also examined video footage of former Prime Minister Tony Blair and Big Brother housemates Adele Roberts and Les Dennis to spot the difference between what they said and what they actually believed.
Professor Beattie, who is Head of the University's School of Psychological Sciences, has been resident psychologist on all 10 Big Brother series on Channel Four.
He said: "This material shows for the first time a behaviour clash between what people espouse openly and explicitly on green attitudes and what they hold unconsciously and implicitly.
"Explicitly, people may want to save the planet and appear green, but implicitly they may care a good deal less.
"Given it is these implicit attitudes that direct and control much of our behaviour in supermarkets and elsewhere, these are the attitudes that we have to pursue and understand and change.
"While speech can be consciously edited and controlled, gestures are difficult, if not impossible, to edit or control in real time, and so the true thoughts and feelings of the speaker may become manifest in the gesture.
"This research shows there are 'green fakers' out there, who say one thing but believe another. We need to work on the hearts and minds of such individuals to produce attitude change."