By Christy Tidwell

The Exorcist. Hereditary. The Ring. Texas Chain Saw Massacre. These are often named some of the scariest movies out there. They’re also among the most popular horror movies, ones that are watched and re-watched, considered classics. Horror movie fans want to be scared, after all.

But what makes these movies – and others like them – so scary? And which is really the scariest?

Since 2020, the Science of Scare Project has run an experiment to try to answer the second of these questions. The project asks a panel of 250 people to watch horror movies while measuring their physiological responses to them and then ranks the scariest movies based on those responses. In past years, they have relied simply on heart rates, but – after some criticisms from horror fans that this emphasizes only one sudden type of fear – they have updated this for 2023. Now their study includes not only heart rate as way to measure excitement and fear but also heart rate variance, arguing that “the lower the heart rate variance the more stressed our audience members became, a good indicator of slow burn fear and dread.”