Frightful films spook fraidy cats.

• Position: Psychological effects of scary films

If you sit with your back to the wall while reading a murder mystery or check all the locks twice after seeing "Friday the 13th," it might be because you are a highly arousable person-someone who tends to be distracted by noise and very bothered by changes in the weather. According to Glenn G. Sparks, associate professor of communication, Purdue University, those individuals who score high on a standard measure of arousability are more likely than others to be trightened for several days or be afraid to go into certain rooms in their home after watching a scary movie or television program.

Those same people, he points out, are most likely to report trouble sleeping after viewing a scary movie. The fright reactions sometimes last for several days, weeks, months, or even years. Moreover, "When we showed these people a clip from the movie, |Too Scared to Scream,' they were much more likely to show increases in skin conductivity and decreases in skin temperature, both of which indicate greater physiological responses."

Of those who...