Joan Smith: The difference between write and wrong

I once emerged from an Underground station to find central London in the midst of a torrential storm. I sent a text to my publisher, telling him I'd be late for a meeting while I waited for the rain to stop, and received a perplexing reply. Was I ill? Should he come and get me? I stared at my mobile, wondering what on earth he was talking about, until I re-read my own message. Predictive texting had changed "rain" to "pain".

I'm sure something similar has happened to anyone who texts, dashes off emails on a smartphone or uses Twitter. I compose tweets on my iPhone, on a keyboard that's two inches by one, and I'd be astonished if I didn't make mistakes. Usually I catch them, but I'm also aware of the brain's ability to see what it expects, rather than what's actually there. When I read Ed Miliband's tweet about the death of the TV presenter Bob Holness, I registered the typing error – "Blackbusters" for "Blockbusters" – and thought no more about it. Sadly, I can't say the same for the people who rushed on to Twitter and composed lame jokes about it. In no time at all, Miliband's Twitter "gaffe" was being discussed as though it revealed something about his character or his ability to lead the Labour Party.

Did Harold Wilson ever make a mistake in a handwritten note? Margaret Thatcher? I don't know, largely because they lived in an age before social media, when their communications would have been scrutinised (if not actually typed) by someone else before being exposed to the world. I hope I'm not destroying cherished illusions here, but publishers employ copy-editors to correct errors by some of their most erudite and successful authors.

In the case of Twitter, there are compelling reasons to think twice before mocking someone's latest tweet. Not long after Miliband's "Blackbusters" error, a political blogger quoted a satirical response that appeared to come from Diane Abbott, whom Miliband had reprimanded a day earlier for a carelessly expressed opinion on Twitter. It suggested that shadow ministers were now "openly taking the piss out of the leader". Shortly after that, the blogger was on Twitter again, acknowledging that this "Abbott" tweet was a hoax. So, it seems, were recent tweets purporting to come from Rupert Murdoch's wife, Wendi Deng.

In this unregulated world, it might be wise to think twice before using a single word or badly expressed phrase as evidence of anything. In Miliband's case, we don't even know for certain that he, rather than someone in his office, composed the tweet that caused this storm in a teacup. Someone is bound to say he should be in total command of everything that's going on in his office, but that would inevitably lead to accusations of control-freakery. That Ed Miliband, he's so worried about his image! He doesn't trust his staff to do anything!

Much has been written about the abuse of social media by assorted bullies, racists and misogynists. What's been less attended to is the way in which platforms such as Twitter encourage responses from an area of the brain that can't entirely be trusted. Instant communication is just that: a fast response that doesn't take into account factual accuracy, conflicting evidence and questions of authenticity.

There is a good side to Twitter, when conversations are conducted civilly and rationally, but sometimes it descends into the kind of name-calling you get at a children's party. Ed Miliband has nothing to be ashamed of in this trivial episode, which simply demonstrates the capacity of Twitter to turn over-eager users into twits.