We know movies aren't real but we buy into them more than we realise, a US neuroscientist has concluded, after studying how we observe the world around us.
Professor Jeff Zacks of Washington University in Saint Louis has spent more than a decade exploring what happens in the brain as we observe the world around us.
Research set out his book Flicker: Your Brain on Movies details how we experience moving images, and how filmmakers have learned to take advantage of the tricks our minds play on us in real life.
Zacks says that far from having to actively suspend belief to enjoy a movie, we're actually applying the same processing mechanism that we use when dealing with reality.
"We have a really hard time discriminating, after the fact, whether an event that we learned about came from our real lives or something we read about or something we saw on a screen."
That the effect isn't happening while we're sitting in the movies, but occurs later, was demonstrated in studies of propaganda films made to motivate US soldiers in WWII, Zacks says.
Soldiers shown a Frank Capra propaganda movie on the heroism of Londoners in the Battle of Britain take the story "with a grain or two of salt."
But two weeks later, they can't remember whether this was information from a source they trust, such as friends or newspapers, one they're sceptical of - their Army bosses.
"That grain of salt has totally washed away."
Movies can evoke strong emotion through the effect of the 'mirror rule'- the inbuilt tendency to imitate actions of another person, whether on screen or in real life.
"Film can give us those effects and can produce them really powerfully because it can exaggerate the visual information that we get.
It's particularly strongly activated in young people who have less developed pre-frontal cortex area of the brain.
"If there's punching and kicking happening on the screen you'll see the kids squirming in their seats," Zacks says.
"Once you see that, if you start looking more carefully at the adults, you'll start to realise that there are little facial tics and little movements that are the suppressed motor programmes trying to get out.
The involuntary effects film and novels have on us isn't all bad, though.
Zacks says one of the benefits and pleasures of fiction is that it gives us insight into what other people do and a chance to think how we might react in a wide range of situations.
"I'm sure we've all had the experience of reading a novel where a character with whom you identify is going off the rails, or seeing this in a movie, and you just want to reach out and shake them.
"In some audiences, in America at least, it's socially appropriate to provide instructions by yelling at the screen to tell this character what they should be doing."