Books are amazing things. When we read fiction, we can get strong emotional reactions. It's so common that we need to step back to even realize that it's mysterious. Why would we ever feel real emotions and laugh because of a made-up story?
The reason is that most parts of our minds cannot distinguish fiction from reality, and those parts react similarly in both cases. Our ancient ancestors experienced only real things -- they had no media imagery. Many of the brain structures we inherited from these creatures are more or less intact in the evolutionarily older parts of our brains today. We held on to our lizard brains.
More recently in our evolutionary history (but still a long time ago), people told each other stories. Language and the imagination worked together, as they do today, to generate simulated experiences in our heads upon hearing stories. We didn't have to wander into that valley to know that there were hostile people there -- we could just listen to someone tell us about those experiences.
Several experiments have shown that we tend to believe what we hear unless specifically told that we are hearing a falsehood, and this makes sense if we accept that the original function of storytelling was to communicate important information about the world. As a result, when we read a work of fiction, the death of a character can make us cry, or a situation can make us laugh because most of our brains think it's real. Just as when we watch a horror movie, we need to keep telling ourselves "it's just a movie," but we can't help but feel scared anyway. We are of two minds -- the older part that believes what it sees, and the newer part that can distinguish media from reality.
So why does anything, be it real or fictional, makes us laugh?
Laughter is normally associated with humor, but most instances of laughter occur in situations where absolutely nothing is funny at all. We don't even notice it, but the careful study of laughter (done by "gelotologists") reveals that laughter most often occurs in pointedly unfunny situations such as when people run into friends they haven't seen in a while. And nobody thinks being tickled is actually funny, but it makes us laugh nevertheless.
So how can we understand laughter, when it appears in such varied contexts as being tickled, seeing an old friend, or watching "Borat"? The best theory we have is that laughter occurs in the wake of experiencing a "benign violation," which means that we laugh when we experience something that is initially frightening or unexpected, but turns out to be safe.
Humor can cause laughter, and though different scholars have different ideas of what makes something funny, everyone agrees that surprise, or a violation of what is expected, is a necessary component. In fact, one scientist managed to get laughs out of people in the lab just by having them lift little buckets -- when the weight was lighter or heavier than they expected them to be, people laughed. Funny!
Tickling, for instance, happens when someone is touching vulnerable parts of your body but is not actually hurting you. People often laugh on roller coasters, because they are getting the thrill of danger in an environment they know, at some level, is safe.
Why would we evolve the laughter behavior? Laughter might be caused by a feeling, but it also has a visible and auditory component. Just as the basic emotions have facial expressions for the benefit of other people, so too laughter can be heard by other people -- and it can even be contagious. This indicates that it also serves a communicative function, perhaps telling others that in spite of appearances, we're actually safe. And it's not just humans. Even rats have supersonic "laughs" when tickled that humans cannot hear, and some scientists think that other primates have analogs to human laughter, suggesting that laughter evolved long ago, before these species differentiated.
The fact that we feel emotions when we watch films shows that we can't help but perceive human characters when all we're looking at is light from a screen. The old parts of our minds think it's real. What's more amazing is that we can get the same effect from the printed word. Fictional stories, encoded in language, can transport us over time, space, and into different people's heads.
Why do we laugh just by looking at some ink on a page? Because in our imaginations we recreate the story, parts of us think it's real, and we react to benign violations just like we do in real life. You can read a frightening story, or an adventure story, from the safety of your living room: it's the pleasure of something that feels scary but is actually safe.
Now there's a reason to laugh with joy.
Jim Davies is an associate professor at Carleton University and the author of Riveted: The Science of Why Jokes Make Us Laugh, Movies Make Us Cry, and Religion Makes Us Feel One with the Universe (Palgrave Macmillan, $27.00). He is the director of the Science of Imagination Laboratory.