Effectiveness of subliminal message

Certain types of subliminal perception (hypnosis, for example) are known to affect the perceiver without any conscious knowledge of the effect on his part. However, there is no strong evidence that the types of messages discussed in this article (ones embedded into normal objects such as posters or movies) are at all effective.

Perception of subliminal messages is a type of subconscious cognition. Unlike unconscious tasks such as attending to one signal in a noisy environment while keeping track of other signals (e.g., listening to one voice out of many in a crowded room) and automatic tasks such as breathing, subliminal message cognition cannot be done consciously.

An important question about subliminal perception is: How much of the message is perceived? That is, is the whole message sensed and fully digested, or are only its main and simpler features? There are at least two schools of thought about this. One of them argues that only the simpler features of unconscious signals could be perceived. The second school of thought argues that unconscious cognition is comprehensive and that much more is perceived than can be verbalized.

Proponents of the power of subliminal messages claim they gain influence or power from the fact that they circumvent the critical functions of the conscious mind, and therefore subliminal suggestions are potentially more powerful than ordinary suggestions. This route to influence or persuasion would be akin to auto-suggestion or hypnosis, wherein the subject is encouraged to be (or somehow induced to be) relaxed so that suggestions are directed to deeper (more gullible) parts of the mind; some observers have suggested that the unconscious mind is incapable of critical refusal of hypnotic or subliminal suggestions.

However, critics of the theory have suggested that the effect of subliminal messages would at best be no more than that of a glimpse of a billboard in the corner of an eye. Controlled experiments that attempt to demonstrate the influence of subliminal messages generally find little to no effect.