Many NLP techniques are based on changing certain qualities (known as submodalities) of a subject's internal images, sounds, and body responses. Prior to the development of NLP, research on these topics was conducted and is summarised in the back of the book Gordon, D., Therapeutic Metaphors, Meta, Cupertino, California, 1978.
Studies have shown that the submodalities in which a client observes a placebo (for example, how colourful the pillbox is) affect the outcome. Other studies suggest that changing the submodalities in one sensory system causes changes in the other sensory systems, as well as emotional changes (thus changing the way your internal picture looks will make you feel different). Office workers in a room repainted blue, for example, will complain about the cold even if the thermostat is set to the same temperature, but will stop complaining if the room is repainted yellow. These are physiological responses, so sounds of around 80 dB cause a 37 percent reduction in stomach contractions (similar to the result of "fear", and likely to be perceived as such, as the writers of scores for thriller movies know). These examples came from the following sources:
Buckalew, L.W., and Ross, S. ,"Relationship of Perceptual Characteristics to Efficacy of Placebos" in Psychological Reports 49, p955-961, 1981
Berry, P. "Effect of Coloured Illumination Upon Perceived Temperature" in Journal of Applied Psychology, 45(4) p248-250
Smith, E.L. and Laird, D.A., "The Loudness of Auditory Stimuli Which Affect Stomach Contractions In Healthy Human Beings" in Journal of the Acoustic Society of America, 2, p94-98, 1930