On the way home from dinner with girlfriends I composed my usual thank-you text. Smashing company, delicious food, must see you all again. A couple of kisses. Feeling this wasn’t enough, I added a line of coloured pictures: an ice cream in a cone, a slice of cake with a strawberry on top, a bar of chocolate, a cup of steaming coffee — near enough representations of the puddings we had shared.

The replies came back: smiley faces, rows of hearts, bowls of spaghetti (it had been an Italian), martini glasses.

My friends and I are in our late twenties and early thirties, yet we communicate using emoji: the sort of cute, pastel-coloured symbols that we’d have been embarrassed to have in our primary school sticker albums. What has possessed otherwise articulate, professional women — barristers, solicitors, doctors, English teachers, financial journalists, all with degrees — to end their text messages and social media posts with pink hearts, sparkly diamonds and glossy apples?

Until a few months ago, I rolled my eyes at smiley faces and bunny rabbits. Throughout the 1990s and 2000s I had resisted emoticons — punctuation marks combined to give an expressive smiley 🙂 or sad 🙁 face. I winced at the texts sent by one boyfriend full of grinning parentheses and winking semicolons. He spoke four languages and he had a doctorate — why did he type like a toddler?

A couple of years ago, everyone I knew bought iPhones, which have more than 700 emoji symbols in bright, cartoon colours. I still had a five-year-old non-smart phone that registered any emoji it received as a series of black rectangles and dots — about as cute as Morse code. But at my computer, on Twitter, I could see them: little can-can lines of sweeties, balloons, hearts and stars. I decided that anyone who used them was an imbecile, an infantilised kidult.

Then, three months ago, my battered old phone with its dodgy battery gave up the ghost. I was persuaded by the persistent assistant in Vodafone to upgrade to an iPhone — and within a fortnight I was suckered.

I joined the photo-sharing site Instagram, where emoji are the lingua franca. I started posting pictures of spring flowers accompanied by little tulip emojis and of lunchtime frittatas with tiny emoji frying pans and tinier emoji eggs.

Emoji were dreamt up in the mid-1990s by Shigetaka Kurita, a Japanese tech developer, as a way of making unfashionable corporate pagers appeal to teenagers. The name combines the Japanese word for picture, ‘e’, with character, ‘moji’. It wasn’t until the advent of the colour-screen smartphone that the idea began its march to world domination.

Billions of emoji are sent every year. A website, emojitracker.com, keeps a running tally of their use on Twitter. The most popular image is the ‘weeping with laughter’ face. In the time it has taken you to read this far — say, a minute — it has been used more than a thousand times. At the time of writing, the total for just this one symbol stands at more than 729 billion.

Some countries conform admirably to type in their emoji use. France is the only country in the world where the crying-with-laughter face is not the most used symbol. There, it is the heart. Oh, l’amour. Australians use double the average number of alcohol-themed emoji. Americans use more meat symbols — drumsticks, burgers — than any other country.

Other nationalities are less predictable. Arabic users are four times more likely to use images of plants and flowers; Canadians most likely to use picture of guns and images of banknotes.

So prevalent are emoji that the White House has started using them across its social media campaigning aimed at millennial voters. Such messaging will appeal more to young female voters than male. Women are overwhelmingly more likely to send emojis than men, according to research from Columbia University. Men, not unsurprisingly, run scared of bunny rabbits and pansies. That could change. There are online petitions for future iPhone upgrades to offer more sports and computer gaming emoji.

For now, though, among the most popular symbols are pink hearts, lipstick kisses, red roses, pink daisies and boxes of chocolates tied with satin bows. You have to go quite some way down the rankings on emojitracker to get to beer mugs and rugby balls.

My theory is that women have adopted cloyingly sweet emoji as protection against the often nasty, combative, bullying character of social media. Hearts and stars are an antidote to 140-character shouting and trolling. Used well, they can be ingenious. I was tickled by a photograph posted by an architecture critic on Instagram, of a sculpture by the American pop artist Jeff Koons, famous for his helium rabbits. The picture was captioned with a red balloon emoji followed by a whiskered rabbit.

Is it possible that future professors of linguistics will pore over our cryptic language of pictograms? Logograms have served the Chinese since the Bronze Age. The Egyptian pyramids were built on hieroglyphs. Is ‘vulture-viper-bullrush’ so very different from ‘kitten-cookie-pineapple’?

Listen to Laura Freeman discuss the smiley-face cult: