When a terror attack strikes, it often leaves people feeling powerless – struggling to find a way to cope, struggling to find a way to respond, struggling to find a way to move forward. This is particularly the case if you haven’t been directly affected by the violence – the tragedy has happened somewhere else but you feel an emotional need to share your thoughts with the world.

Social media can play a very constructive role in these circumstances – sharing your thoughts, responses, feelings with your circles of friends and networks, self-publishing your opinions to the world.

This is a form of collective mourning – it is not limited to the aftermath of terror attacks, but this is a phenomenon that we are increasingly seeing in relation to major public events such as the death of a celebrity, a transport accident, or acts of random violence.

In many ways it is in the interests of social media to fuel this type of collective sharing of emotions. Facebook seems to be the best at this – in the wake of the recent attack on Paris users were encouraged to change their profile photo to the French tricolour, and people who were in Paris could use a new Facebook function to mark themselves as “safe”.

What’s interesting to observe in the midst of this type of collective mourning or collective sharing of emotions is that it displays many of the classic characteristics of mob mentality – there is a peer pressure to join in, those that resist joining the collective activity may feel bullied into doing so, and anyone that dares to present an opinion that is contradictory or not in line with the accepted message on the specific event is quickly vilified and ostracised.

While this type of mob mentality isn’t limited to social media channels (see for example the tradition of wearing of poppies to mark Remembrance Day in the United Kingdom), it is the social media channels that provide the most effective for the immediate outpouring of thoughts and collective sharing of emotions.

There’s an added complexity with social media and the response to major events – how do you know when it is okay to return to “normal” activity? If your normal social media activity is sharing funny videos about cats, or posting photos of what you’re about to eat, when is it no longer collectively considered to be inappropriate or insensitive to resume normal service? It seems as if there are no hard and fast rules about this, but at some stage the momentum of the collective mourning will lose steam, life will go on, videos about cats will once again be shared.

Facebook again seems to be on the front foot with this consideration – introducing the feature of a temporary profile picture. To mark the recent terrorist attacks against Paris, Facebook helpfully suggested to users that they could temporarily add the French tricolour to their profile picture and set a date by which their profile image would revert to the original.

Mob mentality may not be a new phenomenon, but our social media channels are helping to shape the way that we collectively respond to developments around us.