Regarding the pain of others

After Islamic State militants murdered journalist James Foley, they released a video of his beheading, the New York Post put a picture of it on its front page, and millions have shared and seen the video via social media.

From this, to news sources revelling in the intimate details that might have contributed to Robin Williams's recent suicide, to countless websites dedicated to viewing genuine atrocities, to the current trend for "torture porn" in mainstream horror (where the focus is on realistic brutal things happening to people, rather than plot or suspense), it seems people have an endless fascination with horrific and gory details.

Why is this? Why do supposedly normal people seem to revel in witnessing brutal, gruesome things happening to other people? Why do we slow down to stare at car crashes?

There's no clear-cut answer but, as is often the case, there are many theories that offer at least part of an explanation.

At the most basic level, there's the excitation-transfer theory. Seeing or experiencing something so visceral, so brutal, is powerful stimulation. It puts the person in a brief state of excitation, during which other stimulation can be more intense. A comparable example would be riding a roller-coaster; once you get off, you're in that giddy, excitable state that comes from an adrenaline rush, and you feel more "alive". There's complex psychology behind risk-taking behaviour, and people can get hooked on the experience.

It's possible that fascination with gore is a darker, somewhat twisted variation on this. We know it's wrong, we know it's deeply unpleasant and grim, but this "wrongness" provides the same stimulation, so we do it anyway, and get the vicarious thrill. CGI gore may be enough for some, but to see actual, real horror could be even more stimulating, because there's no need to suspend disbelief.

There's also plain old curiosity. What can happen to the human body when it is badly damaged seems to be something many are very curious about. There may be evolutionary reasons for this; an interest in possible dangers and damage is a useful survival trait.

Some would even argue that the morbid fascination for grisly details can be a good thing. Some argue that all people have this dark element to their psyche, this sinister component that seeks out unpleasant details or situations, or even causes them. Repressing this aspect of ourselves could prove more harmful in the long run, whereas exposing yourself to grim sights and details allows you to express it safely, providing catharsis.

Of course, not everyone believes this. And the counter-argument is that fascination with the macabre just gets more potent as you become desensitised to such sights, and you require more intense stimulation to provoke the same response. This is obviously not a healthy way to be.

You could also point to the "just world hypothesis". This is the theory that all people believe the world is fundamentally fair, so when bad things happen to people there's a knee-jerk assumption that they deserve it for some reason.

But there's also the simple explanation that people revel in something so bad precisely because it's so bad. Countless studies have shown that bad things have far more impact on the psyche than good things. Bad things happening are themselves a powerful draw for curious or thrill-seeking humans, and there are few things as bad as another human meeting their untimely end in deeply unpleasant ways.

• Burnett is a psychiatry lecturer at the University of Cardiff