Another theory on perception is Gestalt's Principles of Perception. The three principles are proximity, uniform connectedness, and good continuation. The proximity principle asserts that things that are close to one another are perceived to be more related than things that are far apart. Uniform connectedness deals with perceiving things in groups based on how they are arranged. Good continuation explains how people perceive elements to be more connected if they are presented on a line or curve.
Accessteacher nailed it. People have different lenses which they use to examine, criticize, and evaluate the world around them. These lenses are created and supported through cultural ideals, family preconceptions/stereotypes, and education. For example, people who grow up in the deep South tend to hold perceptions similar to those held during the Civil War. Their culture and family ideologies tend to mold and uphold these lenses (perceptions).
Heuer's work argues that perception is based on a series of mind sets that act as lenses that we perceive information through. Interpretation is different because as people we are unique and culture and other forces mean our perception will be different. This means that how a patient perceives the words of an analyst will vary drastically depending on the lenses of that patient. An excellent example in the context of health would be a patient who comes from a different culture than the analyst and therefore interprets what the analyst says differently because of those cultural lenses.