Sunday, October 30, 2011
Happy Halloween! It's a time of costumes, candy, and for those more thrill-seeking types
, horror movies.
Personally, I'm a total wimp when it comes to scary movies. Show me anything that's even trying and failing to be scary, and it will still scare me. So that got me thinking, why is it you can walk into a movie feeling like this:
And suddenly feel like this:
After all, there's nothing inherently scary about that image. It's just a forest at night. But it's the fact that it's a forest at night in a scary movie
that has me sitting on the edge of my seat. This is a phenomenon called priming
, wherein the fact that I know that this is a scary movie and scary things will happen will make me more likely to "fill in the blanks" of that scene with my imagination. In other words, since I know something scary will probably happen soon after being presented the visual stimulus of the dark forest, I will begin to look for something to scare me in the scene when nothing inherently scary is there at all, while still proceeding to scare the living daylights out of myself.
Film makers are very, very aware of this phenomenon and they love to exploit it. After all, it makes their job a lot easier. If you can scare yourself by just imagining what's happening off-screen, then the film makers don't have to go through all the trouble and expense of actually showing you, and your imagination will almost always come up with something more horrifying than what they can show you on screen, anyway. Movies like Paranormal Activity
and The Blair Witch Project
capitalize on this by showing you shaky, home-movie style shots and lots and lots of scenery without ever showing you the source of the threat throughout most of the movie. The idea is that by presenting these otherwise neutral scenes with the implication of a threat intensifies the emotional reaction of the audience.
So what's actually going on in your brain while this is happening? A recent study
in Social Cognitive and Affective Neuroscience
aimed to figure that out. Researchers observed subjects' brain activity in a fMRI as they read two different types of sentences; one which implied a fearful situation, and another which was neutral. In the fearful type of sentence, none of the individual words themselves were inherently fearful--that is to say that there were no words like "threat" or "hurt" or the like. An example of one of the fearful sentences used in the study is "The boy was never found again."
In the next trial, the researchers showed the subjects neutral images (like a boy on a beach) and paired them with the fearful and non-fearful sentences. In a final trial, the subjects were shown the images again, but without the sentences to see if the emotional memory of the images with the sentences would carry over without the presentation of the sentence.
When subjects were presented a fearful or non-fearful sentence with and without a picture, there were higher levels of activation in subjects presented a fearful sentence with and without a picture than in subjects shown non-fearful sentences with and without pictures. These areas of activation were the middle temporal gyri, the temporal poles, and the left inferior frontal gyrus, which are associated with language processing and understanding.
The researchers also found an additive effect in the right temporal pole when subjects were shown a fearful sentence with a picture (the right black bar) than when subjects were shown a fearful sentence alone (the left black bar).
The temporal poles, which are the front-most projections of the temporal lobe, are still poorly understood in their function. However, they are connected to many structures in the brains emotional, or limbic, system and they have been implicated in the processing of emotion, and binding emotions to linguistic and visual stimuli (such as associating a fearful looking face with feeling fearful yourself).
So far, one brain structure has been conspicuously absent from this study on fear: the amygdala. The amygdala is often referred to as the "fear center" of the brain, so why has it been so quiet up till now? It would appear that the visual stimulus is necessary in this case to cause the amygdala to react to the fearful sentence. Subjects who were shown fearful sentences with images had higher levels of activation in the right amygdala, whereas subjects who were shown fearful sentences without images had no activity above baseline in the amygdala. This would imply that the amygdala does not necessarily interpret emotional salience from language alone, leading the researchers to conjecture that perhaps the amygdala can only be activated in this context with linguistic-emotional binding input from the temporal poles.
The amygdala also has an interesting role in the third trial of this experiment. Researchers showed subjects pictures that were either previously paired with a fearful sentence, a non-fearful sentence, or no sentence at all, and monitored activity in their right and left amygdalae. Pictures that had been previously shown with a fearful sentence led to a higher level of activation in the subjects' amygdalae than did pictures that were previously shown with a non-fearful sentence or no sentence at all. This is in line with other evidence to show the role of the amygdala in emotional memory. That is to say that when the image was previously shown with the fearful sentence, it was "tagged" by the brain as emotionally salient. The presentation of the image again, even without the fearful component, will bring up the emotional flavor of the image, and lead to higher levels of activation in the amygdala. Our brains are excellent at drawing connections between various stimuli in our environment. We can take inherently un-emotional words, phrases, and images and combine them to form context and illicit emotion. So the next time you go see a horror movie, take a moment to observe how artfully (or perhaps artlessly) the movie is taking advantage of and manipulating your own imagination to scare you even more.
Willems, R.M.; Clevis, K.; Hagoort, P. (2011) Add a picture for suspense: neural correlates of the interaction between language and visual information in the perception of fear. Social Cognitive and Affective Neuroscience, 6(4), 404-416.
This post was written by Cynthia McKelvey has also been cross-posted to Notes of Ranvier