The mental process by which a person makes sense of an idea by assimilating it to the body of ideas he or she already possesses. This affects how they perceive the world around them. Likely related to the Reticular Activating System which filters our perception according to certain criteria and belief systems.
Wikipedia: ”A rich child and a poor child walking together come across the same ten dollar bill on the sidewalk. The rich child says it is not very much money and the poor child says it is a lot of money. The difference lies in how they apperceive the same event – the lens of past experience through which they see and value (or devalue) the money.”
The Thematic Apperception Test presents a series of ambiguous images and asks a subject to interpret them, leading the subject to reveal their unconscious biases and apperceptions of the world around them.