Advancements in CGI have made it cheaper and easier to create action sequences and other visual effects that required the efforts of professional stunt crews in the past. However, reactions to action films containing significant amounts of CGI have been mixed as films that use computer animations to create unrealistic, highly unbelievable events are often met with criticism.[4] While action has long been a recurring component in films, the "action film" genre began to develop in the 1970s along with the increase of stunts and special effects. The genre is closely associated with the thriller and adventure film genres, and it may also contain elements of spy fiction and espionage.[5]