A mass experiment which aims to test the emotional intelligence and intuition of people living in the UK has been launched in Edinburgh.
The smile on the left is real, with the one on the right a fake
Professor Richard Wiseman detailed the test at the start of the Edinburgh Science Festival on Friday.
Photographs of people smiling will be on display at the festival, with participants asked to identify which are genuine grins and which are fake.
Everyone taking part will get feedback about their own intuitive abilities.
People can also view the specially commissioned photographs and take part in the study online.
Participants will be asked to complete a short questionnaire on intuition, allowing researchers to examine the types of people who are especially good at recognising emotions in others.
Certain parts of each face will be masked in the pictures to help discover which provide most information.
Professor Wiseman said: "The ability to accurately judge the emotions of others is an essential psychological skill in almost every area of life.
"This study aims to discover who is especially good and bad at this mysterious skill, as well as providing some insight into how people can improve their intuitive abilities."
Prof Wiseman, from the University of Hertfordshire, will announce the results of the Sixth Sense study at the end of the festival on Sunday, 10 April.