It has become one of the hallmarks of the news now. Whenever there is a dramatic event, social media instantly comes alive with comment and conjecture as facts vie for attention with fiction. Alongside the chatter on social media are journalists rushing to report on the news as it happens,
Alfred Hermida: How the rumour factory operates in crisis
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Misinformation sometimes spreads faster than the truth in the public square of Twitter.
In their classic 1947 text, The Psychology of Rumor, Gordon Allport and Leo Postman showed how rumours arise in situations that are important but where information is ambiguous. Under such circumstances, people will grasp at anything that can help them understand what is happening.
Rumours become part of what Japanese-American psychologist Tamotsu Shibutani described as improvised news. It is a way of trying to make sense of things that challenge the everyday.
Shocking events such as the Sydney siege are viewed through an individual's personal lens but that view is shaped by what else is in the public consciousness. It is hardly surprising that some concluded the attack was linked to Islamic extremism when a banner with Arabic writing appeared in the cafe window. Headlines across the world have been full of talk about Isis (Islamic State) and the threat of homegrown extremism.
People were primed to jump to conclusions and speculate about the causes of the attack. There was similar speculation about the shooter following the attack on Parliament Hill in Ottawa in October. The conditions have to be right for an idea to catch on, especially on social media.
Given that breaking news fosters fertile ground for rumours, half-truth and lies to spread like wildfire, there is an imperative for all of us to be mindful of what we hear, see and read before hitting that retweet button.
The exchanges on social media are conversations about information in flux. At times, it will be people collectively trying to figure out what happened and who was responsible. Some of it will be true, but some of it will be wrong.
Social media is the new public square where people get together to talk about the news. In the square there are some in the know. Others are sharing hopes or fears. Others have come there for emotional support. Some just want to be part of something bigger.
All this chatter is part of the news now. It is part of a media space where the news is improvised, and a hodgepodge of real-time facts, fears and fictions.
Alfred Hermida is associate professor at the Graduate School of Journalism at the University of British Columbia.