Horror movies do something strange and incredible to your brain

"Usually when we're watching something we've shut down the motor regions of the brain, and yet those stimuli [from a shocking scene] are so strong that they overcome the inhibition to the motor system," says Michael Grabowski, an associate professor of communication at Manhattan College and the editor of the textbook "Neuroscience and Media: New Understandings and Representations."

We jump or yell because a film bypasses our tranquilized state and taps into a primal instinct, which is to react immediately to protect ourselves and warn others — before taking time to process what scared us. "The scream is a way to alert others in your social group and scare off attackers," says Grabowski. Grabowski's background is in filmmaking, but his research now is focused on an emerging field called "neurocinematics," which focuses on the connection between the mind and the experience of cinema.