If you've ever seen a horror film, you've likely experienced a jump scare. A mix of cinematic build-up, sonic tension, play on expectations and intent to scare, the jump scare is a classic building block in horror movies with one goal: catching the audience off guard and making them jolt. But what makes a good jump scare? Why do they feel so different today, than what it was in the past? From 1942's jump scare pioneer 'Cat People' to more recent films like 'It' and 'Smile,' here's everything you need to know about the craft behind the horror technique and its need for constant evolution.