What did market researcher James Vicary do in 1957 that made people concerned about subliminal manipulation?

In 1957, James Vicary falsely claimed that he conducted an experiment on 45,669 individuals who are moviegoers at New Jersey theater. He reported that it exposed the individuals to a split second advertising of pop corn and coca cola and that this dramatically increased the amount of pop corn and coca cola that was sold. This type of advertising is called subliminal manipulation. It was later discovered that James was lying.