Sunday, October 30, 2011

How film makers are using your own imagination to scare you

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:
See 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.

Movie Magic!

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.

The Science

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.

The Results

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.
Brain activity in people presented with fearful sentences
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.

Images courtesy of ragemaker, we <3 it, and Social Cognitive and Affective Neuroscience
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.

Sunday, October 16, 2011



I grew up in the North--first New Jersey and then I went to college in Oberlin, Ohio.  So when I recently moved down to Florida to start a new job, one of the most exciting things I found about my new location was the new fauna.  Particularly all the little lizards running around!  The most common lizards to Florida belong to the Polychrotidae family, and are generally known as Anoles.  However, "lizards" are a broad and diverse group, with many different species with very different morphologies and life styles.  Here are a few fun facts about lizards:

  • Lizards hear through the conduction of sound through small bones in their lower jaw vibrating a tympanic membrane (sometimes visible on the outer skin surface)
  • Some lizards have prehensile (grasping) tails that aid them in climbing.
  • Other lizards have more elongated tails that they can use for defense as whips.
  • Some only have two limbs, while others are limbless (not to be confused with snakes).
  • Some have webbed limbs and even specialized skin flaps that act as parachutes or gliders (I highly recommend that you go and watch that link, it's a really cool video from Animal Planet that I couldn't embed here.)
  • Some have specialized fringes on their toes that allow them to run on water!  (See video)

However, being a nerd I find one of the most intriguing things about all lizards is that--unlike us--they are ectothermic, or basically cannot internally regulate their own body temperature.  This is what is generally referred to by the term "cold-blooded," although that term is considered a bit archaic by the scientific community due to the fact that cold-blooded animals do not have cold blood.  In fact, most of the time lizards probably have blood that is warmer than the blood of "warm-blooded," or endothermic animals (i.e. mammals and birds).

In order to understand the implications of being ectothermic, we should first consider the importance of body temperature in general, regardless of how it is regulated within an organism.  At it's most reduced, life is the result of many physical and chemical interactions occurring within the cells and tissues of the body.  The chemical interactions in particular (such as the transcription of DNA into RNA, and the translation of RNA into proteins; the breakdown of proteins and fats by enzymes; and the break down of ATP into ADP for energy... the list goes on), will function most efficiently within a certain temperature range.  If that temperature is too low, for example, then all those processes happen much slower.

What is it like to not be able to physiologically regulate your own body temperature?  Well for one, it vastly limits the type of environment you can live in.  While there are a few lizards that live in higher latitudes and altitudes, most lizards live in very warm climates.  This is because in order to keep their body temperature within an ideal range (somewhere around 40° C), they have to bask in sunlight and on warm substrates to keep warm, and then get to shade or be able to bury themselves in colder dirt or sand when the surrounding environment gets too hot.  In this way, you could consider lizards as behaviorally regulating their own body heat, but they still lack the physiological mechanisms by which endothermic animals regulate their own body temperature.

As you may guess, the environment ends up playing a very large role in determining the lizard's activities throughout the course of the day.  But as with any trait, it wouldn't have lasted so many generations if there wasn't a significant benefit.  Endothermic animals, in order to maintain their high internal body temperature, must have a very high metabolism to produce enough heat.  This high metabolism needs to be powered by energy gained from food, so a significant amount of the animal's time and energy must be allocated into foraging just to maintain their metabolic rate.  Lizards and other ectotherms don't have that problem; none of their energy intake needs to be put towards generating heat, so they can spend less time foraging and thus can allocate their energy towards rapid growth, social behavior, and reproduction.

The social behavior is what personally intrigued me by the Anoles of Florida.  If you watch these little guys for more than a few minutes, you will probably see them bob their heads up and down and extend a red projection from their neck, known as a dewlap.  This general behavior is seen in male Anoles, and is thought to serve to both establish territoriality and dominance over other males, as well as to attract females.  Moreover, the specific factors such as number of body push-ups, head bobs, and the degree of extension of the dewlap can convey specific signals within the same species of Anole.  It is also thought that the color of the dewlap varies between species, and that Anoles are able to visually detect the differences in color.  Some lizards are even capable of detecting ultraviolet wavelengths, thus adding another dimension to the visual spectrum that we cannot see ourselves.  Accordingly, the dewlaps of these lizards are able to reflect UV light.

In addition to being able to communicate with each other visually on a wider spectrum of visible wavelengths than we can, lizards (and many other animals) are also able to communicate using chemical signals called pheromones.  While the jury is still out on whether or not humans use pheromones to communicate, it is pretty well known that lizards can emit and detect such chemical signals.  In lizards, there seems to be some differences in the methods by which the two sexes employ the chemical signals.  Males seem to emit pheromones to communicate with other males, whereas females use their pheromones in a more male-directed fashion.  Lizards are able to detect these chemical signals using their olfactory system (sense of smell,) their gustatory system (sense of taste) and another sensory system a little foreign to us, the vomeronasal system, which specifically detects pheromone chemicals.  In lizards, the vomeronasal ducts open to the mouth, and they use their tongues to pick up the chemicals and then flick them over the olfactory and vomeronasal ducts.  This is the underlying reason for the tongue flicking behavior that you probably associate mostly with snakes.

There is quite a bit more interesting information about lizards, particularly in the shapes of their skulls and how sound is conducted through their lower jaws.  But in the interest of not writing a whole book on the matter, I'll cut this post off here.  But now you know a little more about the crazy lives of lizards!

Reference and disclaimer
Most of the information I find for the posts I write on this blog comes from a combination of knowledge that I gained through classes and through internet sources.  I generally link to these internet sources in the text of my posts, but sometimes I also get information from books (those archaic sources.)  Most of the information from today's post came from Lizards: Windows to the evolution of diversity by Eric R. Pianka and Laurie J. Vitt (University of California press, 2003).  The rest came from my own notes or internet sources where linked.

Thanks for reading!