Emojis are being used to create secret languages and codes within friendship groups and family chats.

In the new lexicon, pictures of pizza or wedges of cheese popping up on a smartphone might mean 'I love you'.

Apparently, a bathtub symbol offers a different message, which scientists say translates to ‘coffin’.

An even more obscure meaning is attached to a 'thinking face' emoji. Because of the position of the thumb and forefinger on the chin, it mirrors the American sign language symbol for 'lesbian'.

A team from Goldsmiths University of London and the University of Birmingham conducted a survey to investigate how people use emojis and what the real meaning behind them is.

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Other examples which came up during the research included an octopus emoji for 'cuddles' and a devil image for 'I’m feeling sexy'.

In once instance, a balloon followed by a comma and a teddy bear meant 'I’m thinking of you but don’t have the words to say it'.

Of the 134 participants, 74 reported “repurposing” 69 different emoji for private communication.

Dr Sarah Wiseman, a lecturer in computer science at Goldsmiths, said: “Our study shows that people use emoji in a similar way to nicknames or slang, as a handy shortcut to what they mean, which through consistent use creates an intimate ‘secret language’ others don’t understand.

“Creators of emoji need to bear in mind the subtle way that people repurpose them and the impact even small visual changes to them could have on these alternative meanings.”

In 2016, Apple faced a backlash after changing the appearance of its peach emoji.

An investigation found that most Apple users were using the emoji to refer to buttocks, with only seven per cent employing it to describe a fruit.

Dr Wiseman added: “While we know some fruit and vegetable emoji have been repurposed by many people to mean something else, we were intrigued to find out about personal instances of this – examples of emoji that have a special meaning for just two people.

“Often this was about more than just typing something more quickly: people found that by using emoji they could convey very complex meanings and thoughts with them that could not be described in words.”

The findings are due to be presented at the Computer Human Interaction 2018 conference in Montreal, Canada, in April.