They are passed on by word of mouth, through text messages, chain emails and Facebook posts, and in that process they evolve and thrive.

London - Most of us would admit that eavesdropping can be engrossing.

But we might not realise just how much of our attention it commands.

A study found that people listening to two women chatting were so fascinated that they failed to notice a man chanting “I am a gorilla” over the conversation.

More than two thirds of those eavesdropping on the women failed to notice the man, who repeated the words for 19 seconds.

The researchers said it was an example of how intense conversation can leave us “deaf” to the world around us.

A famous study from 1999, in which people watching a basketball game failed to spot a man walk through in a gorilla suit and beat his chest, revealed how focusing on one thing can leave us “blind” to events happening right in front of us.

But this study, from Royal Holloway, University of London, is the first to show that hearing is similarly affected.

The researchers placed two men at a table in a room and two women at another table and recorded them talking about getting ready for a party. Some of their conversation overlapped. Halfway into the recording, a man walked through the room, repeating the phrase “I am a gorilla”.

The recording was then played to a group of volunteers. Some listened to the women’s conversation and others to the men’s, believing they would be asked afterwards about what had been said.

In fact, they were asked if they had heard anything unusual – and only 30 percent of those listening to the women spotted the interloper, the journal Cognition reports.

Lead researcher, psychologist Dr Polly Dalton, said: “This research demonstrates that we can miss even very surprising and distinctive sounds when we are paying attention to something else. We were surprised to find such extreme effects with a listening task because people often think of hearing as an ‘early warning system’ that can alert us to unexpected events that occur out of sight.

“This has real-world implications in suggesting, for example, that talking on your mobile phone is likely to reduce your awareness of traffic noises.”

However, almost of all those listening to the men’s conversation heard the “gorilla” man.

The researchers said they could have been more “tuned in” to a male voice. He had also been slightly closer to the men’s table. - Daily Mail