The mere-exposure effect is a psychological phenomenon by which people tend to develop a preference for things merely because they are familiar with them. In social psychology, this effect is sometimes called the familiarity principle. The effect has been demonstrated with many kinds of things, including words, Chinese characters, paintings, pictures of faces, geometric figures, and sounds. In studies of interpersonal attraction, the more often people see a person, the more pleasing and likeable they find that person.
Gustav Fechner conducted the earliest known research on the effect in 1876. Edward B. Titchener also documented the effect and described the "glow of warmth" felt in the presence of something familiar; however, his hypothesis was thrown out when results showed that the enhancement of preferences for objects did not depend on the individual's subjective impressions of how familiar the objects were. The rejection of Titchener's hypothesis spurred further research and the development of current theory.
The scholar best known for developing the mere-exposure effect is Robert Zajonc. Before conducting his research, he observed that exposure to a novel stimulus initially elicits a fear/avoidance response in all organisms. Each subsequent exposure to the novel stimulus causes less fear and more interest in the observing organism. After repeated exposure, the observing organism will begin to react fondly to the once novel stimulus. This observation led to the research and development of the mere-exposure effect.
In the 1960s, a series of Robert Zajonc's laboratory experiments demonstrated that simply exposing participants to a familiar stimulus led them to rate it more positively than other, similar stimuli that had not been presented before. At first, Zajonc looked at language and the frequency of words used. He found that overall positive words were used more than their negative counterparts. Later, he showed similar results for liking, pleasantness, and forced-choice measures from a variety of stimuli, such as polygons, drawings, photographs of expressions, nonsense words, and .