Does subliminal perception really occur? Can anyone be able to observe something involuntarily without being conscious about it? These questions were raised to challenge the scientific validity of such claims. Experiments were conducted to prove that subliminal perception was indeed a fact.

Messages were flashed briefly and fast to the test subjects by the researchers. The subjects did not report seeing any of these. The subjects were asked whether they 'saw' the material that they did not 'see'. The subjects appeared to 'see' what they actually did not 'see'. But then this could neither be confirmed, nor could it be verified whether the subjects were either mistaken or even lying about seeing the flashed messages.

For example of subliminals, running on your computer screen (designed for self-help) you can search on Google and download program named Subliminal Flash (by Ded Pyhto, Inc).

The experiments came to be considered comical due to the difficulties encountered in both methodology and semantics. But the few devoted researchers continued their search. 'Subliminal perception' after all these was concluded to be an oxymoron by the scientists who were researching perception.

Charles Eriksen, a leading important critic, pointed to a number of flaws in the concept. However, though upsetting, the critique was inconclusive. He concluded that subliminal perception, rather than a question to be proved empirically, was actually illogical. He also did not take into consideration the distinction between the conscious awareness and verbal reporting of the stimulus itself.

According to him, if the subject was able to discriminate the stimulus in a test and therefore become aware of it, then the experiment was treated as failed. That the subject did not see the stimulus was considered by him as not pertinent. However, this critical factor becomes important subsequently to the understanding of illusions, perceptual bias and subliminal perception. On the other hand, these disapprovals by Eriksen and others led to methodological improvements later and finally to the very recognition of the experience.

Though these experiments were unsuccessful in some ways in terms of behavioral and introspective measures. The experiments were not lacking in results but were failures due to the weakness in their integration with available conceptual models and interpretations that lacked clarity.

The earlier Vicary's "eat popcorn" projector studies had exaggerated claims. These claims were acknowledged by many in the beginning of subliminal research despite the fact that Vicary himself considered it to be a weak technique. In the 1960s the debate over subliminal perception was considered dead by the discerning students of psychology. Rather than alarming claims, these were closed as a debunked hoax. However, this was not to be.

N.F. Dixon brought out an inclusive review of the research till then after a decade of Eriksen's upsetting assessment. Dixon, though relying on the same data that Erikesen depended upon, gave a different conclusion. He pointed out that though the information processed were devoid of awareness; the responses were in reaction to external stimuli which were not acknowledged.

Dixons' review gave impetus to Wilson Bryan Key who had laid claims to subliminal perception that led to a wave of fear particularly by Vance Packard, a social reviewer, who cautioned the creation of advertisements by advertisers using psychoanalysts. Key worked further following upon this social critic. This fear exists to the present day.

In subsequent years, the research on subliminal perception took a turn with the acceptance of the fact of unconscious information processing of the human mind besides the conscious information processing. The unconscious information processing differs from the conscious in some respects at the level of cognition (thoughts) and affects (feelings).

We see a figure against the backdrop of a scene that we are watching. At any point of time we observe only one interpretation. This has been established with the use of different perceptual illusions, for instance, reversible figures. The scene is then brought to the level of consciousness. The stimuli are grouped by the mind into outlines in line with how we interpret the scene as established in psychology.

Experiments in subliminal perceptions initially indicated that we see patterns and figures in the ground though we may not have observed these patterns. The processing of conscious and unconscious thoughts is different. This is because the level of patterning of figure-ground organization that is required in conscious processing of features in perception is not required in the unconscious or preconscious processing.

The unconscious or preconscious processing is carried out by connecting resemblances of features instead of interpreting the meaning that we might observe in the background image that we attribute it with. Psychoanalysts interpret this as the 'primary process' of the 'unconscious mind'.

Unnoticed words or images then go through limited semantic and lexical analysis activating temporary motivational states or influencing preference in unclear decisions which then become visible as associated images in free association or dreams. This reasoning is behind the claim that advertisers are likely to implant pictures in ad for influencing the viewers. The important issue is to what extent this is possible and with what impact.

The New Look movement emerged in the 1970s based on the efforts of Jerome Bruner amongst others during the 1940s and 1950s in the studies related to the effect of values and needs on perception. This movement provided the basis for a revival of interest on the topic.

Marcel's string of experiments on subliminal perception in cognitive science was perhaps the most significant. Marcel used demonstrated semantic priming with the use of pattern masking. The methodology deployed in these studies was subsequently improved with the criticism of Marcel's studies. This later led to the critics' acknowledgement of subliminal perception as a distinct reality.

However skepticism abounds with the allegation that advertisers sold subliminal audiotapes which could not be substantiated. There have also been the ridiculous allegations that there is a global plot to conceal the positive research data on these.

But the possible influence of unheard or unseen messages can also not be out rightly discounted. Though this may sound cynical, yet this is not sufficient reason not to continue building upon the present studies.

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