Experience makes us more efficient and predictive perceivers. My husband, for instance, spends hours poring over maps; as a result, he can recognise several seas and countries by their contours alone. In my role as an English teacher, I have read so many student texts that I can identify misspelt words more swiftly than my husband, who as a Maths teacher has developed other (possibly more useful) perceptual abilities. In the same way, a person who takes an interest in a particular brand of clothing can recognise another person wearing that brand, even from a distance. These are all examples of how one’s emotions, motivation, training and experience can influence one’s perceptual set. Another term for this is perceptual expectancy.
Perceptual set refers to a readiness or a predisposition to perceive a visual stimulus in a particular way. Your background, knowledge, motivation and emotions all affect what you pay attention to, which features of a stimulus you focus on and, conversely, which details you ignore. You bring your own expectations to any perceptual task; the context in which you view the stimulus also plays a role. All of these factors allow you to formulate perceptual hypotheses more quickly and accurately, which influences your interpretation of the scene before you and generally enhances your perceptual skill.
For example, in the visual stimulus below, you presumably perceive a horse.
The following picture, however, provides more context. When you look at it, assuming that you have experience of chess and can therefore be influenced by the other figures surrounding the “horse”, you are likely to perceive a “knight”. In this case, both the context provided and your cultural and educational experience work together to influence your perception of the stimulus and your interpretation of its meaning.