When my daughter was four, she made friends with another little girl, two years younger than her. Whenever they met in the street, they would call out each other's name as if they were long-lost relatives reunited for the first time in decades. Then they'd rush together and hug extravagantly. 

The odd thing about this was that they only knew each other from passing in the street. This was the sum total of their relationship.

I found this funny, of course — and so did the other girl’s mum; but I also found it rather touching, this extravagant, unselfconscious display of affection — because it differed so much from my own childhood experience.

In Sunderland in the 1970s, Jewish people didn’t hug and kiss each other socially. A cordial handshake on Shabbat was the closest physical contact you were going to get with anyone you weren’t related to.

So, as an adult, it took me a long time to work out how to embrace my friends. Should it be one kiss? Two kisses? A hug? Nothing at all?

When I was at Cambridge, I learned to kiss on both cheeks. (I had posh friends there). Now, among, my London Jewish cohort it’s one kiss — and hugs for people you’re close to. But even then, there are innumerable subtle variations from person to person, and there’s the constant possibility of getting it wrong, and having an awkward moment where you both flail about, lips and arms making contact in all the wrong places.

The confusion can become even worse once different religions come into the mix. My friend Rachel was attending a Catholic wedding and, not being familiar with the rituals, she took her cues from the people around her. So when the congregation was told to greet the people near them, she watched carefully as the man next to her turned to the woman on his other side and kissed her on the lips. Rachel, assuming that this was the Thing To Do, did the same to him. It turned out, of course, that the man and woman were married.

The French, obviously, have this whole business down to a fine art. I was astonished and impressed when visiting an old friend in Paris recently that his four small boys, none of whom I’d met before, filed past me solemnly when I arrived and kissed me on either cheek.

But what about kisses in writing? When it comes to signing off texts and emails with “x’s”, a whole new world of problems opens up.*

As a young adult, I was in the habit of adding extravagant rows of kisses at the end of messages to my friends. This became something of a reflex, with the result that when I was a brand new editorial assistant in my first publishing job, I accidentally typed “Susan xxxxxxxxxxxxxxxxxxxx” at the end of an email to one of the directors.

The moment I pressed “send”, I realised what I’d done. I sat there, frozen in horror.

Once I had started breathing again, I realised I couldn’t just pretend it hadn’t happened. I had to make clear to the director that the kisses were due to a moment of thoughtlessness, and not to a startling lack of awareness of appropriate communication etiquette.

So I put my head round her office door, red-faced, and mumbled an inarticulate explanation. Given that she was far older and more experienced than me and in a position of power, this was her cue to be amused and reassuring and make me feel much better.

She wasn’t amused or reassuring; instead she was bemused and condescending — which is why I am still trying to get over the trauma 20 years later.

When it comes to epistolary kisses, women are much more keen on them than men. I know this because I carried out some watertight statistical research on the subject: I checked the most recent 10 text messages I’d received from female friends and the 10 from male friends. 7/10 of the women signed off with at least one ‘x’ but only 2/10 of the men did.

The number of kisses matters, too. One kiss could mean you’re writing to anyone from your mother to a close business contact. Two or more are reserved for family and good friends. A row of them, interspersed with circles to represent hugs, means you are 12 years old.

I write most of my messages on my phone using voice recognition, so if you come across me with my phone to my mouth saying, “love-Susan ex-ex-ex,” this will be why. It does sound a bit like I’m walking along saying, “sex sex sex” into my handset — but I’m not, so there’s no need to cross the street to get away from me.

*While researching this subject, I Googled ‘XXX’, which didn’t get me quite the list of results I was expecting.

@susanreuben