Professor Clare Brant of Kings College, London

Oscar Wilde quipped famously that keeping a diary meant he always had something interesting to read on the train. Inside that joke is one of the big reasons to keep a diary: as one app puts it, a diary remembers things for you. Appointment diaries keep track of what you did; expressive diaries keep track of who you were or thought you were when you did it. The Great Diary Project at Bishopsgate Institute, which is partnering the Centre for Life-Writing Research at King’s College London in an exhibition about diaries, has one diary at the back of which is a list: BOYS I HAVE FANCIED. The writer was 13; the year was 1978. It’s quite a long list. I don’t think I can remember everyone who I fancied when I was 13: can you? So a diary can act as a prosthetic memory, extending our range of recall. In an age when dementia is an epidemic, diaries can perhaps help slow some kinds of forgetting.

Diaries can be useful for self-development. Another diarist in the Great Diary Project archive wrote that he was going to chronicle all his doings and mis-doings of the coming years. Poignantly, he wrote ‘There are some things that I don’t care to tell my friends, for one thing, it wouldn’t interest them, then again, I am not of a confiding nature; but it will be nice to have a friend to tell everything to’. A diary can be a loyal friend, especially if you’re young or shy or vulnerable: you can tell it anything and it won’t judge you. There’s now such a split culture: on the one hand, everyone shares their bright shiny lives, and on the other, many of those same people face anxiety, panic attacks and depression. Confiding feelings, doubts and fears to a diary bridges some of the gap. Writing the stressful stuff down can help you understand it – and overcome it.

A relatively recent form of diary invites you to zoom in on an emotion, usually gratitude, though there are variants about like ingratitude or disappointment. What five things are you grateful for today? Again psychologists have done research to show that focusing on positives makes you feel happier: it reduces stress and improves mental health.

One of the big changes to diary culture in the twenty-first century is a move from private to public, paper to digital, though paper diaries are still very popular and online diary platforms have a range of privacy options which let you restrict readership. When the first online diary began in 1995 its writer, Carolyn Burke, who put her whole life out there for anyone to read, made a courageous stand in favour of what she called honesty and freedom therapy. Now it’s the new normal to share aims and aspirations with others, in the hope that communities of readers – who are themselves sharing their goals – will help keep you on track. The surveillance of peers provides support for losing weight or taking up exercise.

Digital forms of diary also create community. From the blogs of travellers who can share the excitement of their adventures to the global reach of celebrity vloggers, that community is newly mobile: you can pick it up anywhere with a signal. This connectivity makes for new forms of relationships and sociability, where instant and frequent postings intensify a sense of closeness. With so much following and liking and sharing, could there be an overspill into more empathy and understanding? With so many people describing their everyday lives in such detail, will we come to understand people differently?

fIt’s easy to make a grand narrative which says the diary began as a private genre and gradually turned into a very public genre of blogs, vlogs, Facebook, Instagram, Pinterest and Tumblr all vying for attention and custom. There’s some truth in that, but there are also parallel histories which work in reverse. Puritan diaries were circulated in communities of believers and read admiringly by strangers who were grateful to discover they were not alone in their struggles against sin. You might also make a history in which seventeenth-century diaries were very engaged with the world - at the start of his diary Samuel Pepys is aware of the crisis facing the nation in 1660 - whereas you could say that in the twenty-first century many digital self-stagings are individualised atoms of disconnection.

But diaries tend to disarm you – even narcissists can reveal a human side. The most banal-looking posts say something about everyday life, including the way banality is part of everyday life. One random Instagram hit I saw recently was someone saying they had bought a new cereal; the photo depicted it. Now you could class this as attention theft – how boring can it be to look at someone else’s bowl of cereal? But it was an attractive photo in a zeitgeist style, an overhead shot of a white bowl with mug unexpectedly placed to the left of it – why? Is this a left hander? – and it perfectly inscribes a sociological moment – yes, it has gluten-free cereal, almond milk and sharing breakfast in a food porn way. Cultural historians of the future may be grateful for all its on-trend tags about healthy eating, exercise and self-love; as a literary critic I am fascinated by the post’s use of emojis, its mix of confession and control, and its floaty position somewhere in the middle of time between yesterday and tomorrow.

So is reading diaries good for you? Since a paper diary is usually private, it’s often assumed that reading it must be voyeuristic. Many diarists have a distant idea of posterity and a mysterious relationship to it: in an Oscar Wilde way, the only thing worse than being read is not being read. There is also a substantial body of research which shows that reading is good for readers. You can increase your powers of attention and empathy by reading. Why wouldn’t this be true of reading diaries too? In an experiment to measure the benefits of reading, scans showed greater connectivity in the left cortex of students who read fiction. Psychologists think that fiction conveys the differences of other people through stories. Diaries tell stories - the stories we tell about ourselves. In diaries on paper, the otherness of someone else is conveyed through their handwriting, their choice of pen, of volume, of how they use the printed pages. In digital diary writing, similar personalisation comes through choice of platform, font, colour, layout and decisions of style. Diaries have plotlines unfolding (and sometimes disappearing with no explanation), and a strong emphasis on voice. Whether paper or digital, they are texts in a rich and evolving genre, both documents of individuality and shared social history. Writing and reading them may be good for you.

By Professor Clare Brant, Department of English, King’s College London 

Dear Diary: A Celebration of Diaries and their Digital Descendants Inigo Rooms, East Wing, Somerset House, London, will run from 26 May – 7 July 2017, 11-5.30 pm Wednesday – Sunday. Find more information here. And more information on Diaryfest : A day of diary-related talks, here. The event is free but booking essential