Subliminal messaging is a method covered with mythical mist. Throughout history there have been a lot of examples where subliminal messages have been placed mainly in movies (or short films), where the message has been flashed for a very short time. So short that its only the unconscious mind that detect it.
Throughout history there have been a lot of experiments with subliminal messaging and all experiments claim that subliminal messaging has an effect. But a very important part of a scientific testing is the documentation of what you have been doing so that the test can be reproduced with the same results.
In 1957 when Vicary claimed that during the presentation of the movie Picnic he used a tachistoscope to project the words “Drink Coca-Cola” and “Hungry? Eat popcorn” for 1/30 of a second at five-second intervals. Vicary asserted that during the test, sales of popcorn and Coke in that New Jersey Theater increased 57.8% and 18.1% respectively. The problem with this is that even though this test has been reproduced in Germany (where they, at lest used to, have a break between the commercials and the film) but without any similar effect.
The conclusion so far is that subliminal messaging do not has a proven effect beyond a placebo effect.
But if you read the piece in Wired magazine about how Ads Implant False Memories into your brain the different effects of an advert on the brain is not fully understood. And many feels there is a connection between what we see in professional hypnosis and subliminal messages.
But since it’s by law is illegal to use subliminal messaging in most countries the use is still restricted to the laboratories…