How to identify if someone is lying: do they say 'I'?

The language people use in the messages they write can be far more revealing than they realise, scientists say, denoting when they are lying or guarding a secret.

A US university study found that those who were concealing an awkward truth used more deceptive language, more negative emotion words and fewer words such as “I” and “me”.

The length and quantity of the emails can also be a clue, as those with a secret wrote more and longer emails after acquiring it than before.

The tell-tale signs of lying were revealed in a study by researchers at Carnegie Mellon University in Pittsburgh, Pennsylvania, which recruited 62 adults who admitted to concealing a life-altering truth.

More than half were keeping a romantic or sexual secret, while others were hiding something related to their family, mental health, job or the law.

The researchers trawled through a year’s worth of their emails, including some from before they acquired their secret.

Their findings, reported by Scientific American, were in keeping with those of another study on the subject by researchers at the University of Texas in Austin.

James Pennebaker and colleagues studied the emails of women who suffered depressive episodes, which they were likely to want to hide from their friends.

They found that the women sent more emails and used more words in them when depressed than when in remission, and more than other, healthy women.

They also used fewer words expressing negative emotions, more positive emotion words and more words like “I” and “me.”

Dr Pennebaker said: “People who are depressed spend much of their time masking it. “They use communication strategies to come across as chipper.”

Both studies were presented at the American Psychological Association annual convention last week.

In previous research, Dr Pennebaker and his colleagues found the language used by politicians and others in the public arena can also reveal secret-keeping.

President George W. Bush used fewer singular pronouns, such as I, me and my, in the months leading up to the invasion of Iraq.

President Harry Truman did likewise before the US dropped the atomic bomb on Hiroshima.

Dzokhar Tsarnaev, the alleged Boston Marathon bomber, included far fewer uses of the first person pronoun in his Twitter messages from October 2012 onwards, which was just after his brother Tamerlan returned from a trip to Russia and allegedly started posting extremist material on YouTube.