Double Exposure

The term "subliminal advertising" referred to and used by the murderer was actually invented by market researcher James Vicary. Vicary claimed that for a movie called "Picnic" playing at a theater in Fort Lee, NJ, he had inserted frames into the film that read "drink Coca-Cola" and "eat popcorn" that were flashed briefly on screen every five seconds during screenings. Though the duration of each flash was too short for anyone to consciously detect, Vicary claimed that this subliminal exposure boosted Coke sales by 18% and popcorn sales by 58%. Advertisers, the FCC, and research psychologists were skeptical, and in an Advertising Age article, Vicary admitted that he had never conducted the subliminal "experiment" - it was concocted as a gimmick to attract customers to his failing marketing business. The concept of subliminal advertising, nonetheless, has continued on as part of our culture.

When Columbo arrives at a back office with monitors, he's being tracked by a videocamera. He arrives and sees himself live on the monitor, filmed from behind. What he sees doesn't match with his actual position, judging by a hand resting against a wall.

References High Plains Drifter (1973)