Psychology -> Gestalt Principles
The stop sign is designed with the concept of figure-ground in mind.
Organisation in visual perception as evidenced in art, signs and symbols.
The Gestalt school of psychology was developed by a group of German psychologists in the early 1900s. The Gestaltists believed that sometimes the whole is greater than the sum of its parts. By this they meant that we take smaller parts and gradually build them into a whole. Thus, Gestalt is a German word for 'form' or 'shape'. As with 'bottom-up' processing, we start with the smaller parts and put them together to eventually form a shape. The Gestaltists named many principles which assist us in this process however, you only need to know these four in preparation for the exam.
Figure-ground: Some aspects of a stimulus appear to stand out as the figure against a plainer background. For example, many road signs make use of this principle so a message can stand out and be seen easily by drivers. The stop sign is designed with the principle of figure-ground in mind. The word 'stop' is the figure, printed in white, against a plain red background. This makes the message very clear to see for the approaching driver.
Closure: This involves the completion of missing contours so that we perceive a consistent overall form. For example, cartoons characters are often a series of lines and incomplete figures, however, we fill in the gaps.
Similarity: This is when elements that are similar tend to be grouped together. For example, members of the police force at a football game wearing the same uniform, will be seen as belonging to one group.
Proximity: We perceive elements which are near one another as belonging together. For example, sheep grazing close to one another in a paddock would be seen as a group.