The roots of horror films began in the late 1700s as an extension of gothic literature from the UK and US, referring to settings in medieval buildings. [1] The introduction of sound in the late 1920s transformed horror films by adding impact. [2] From the 1960s, the genre exploded with new styles and films like Psycho that shocked audiences. [3] Modern horror uses more CGI effects and psychological themes remain popular, though desensitization has increased tolerance for graphic violence.