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 a person is seen by someone, the more pleasing and likeable that person appears to be.
The earliest known research on the effect was conducted by Gustav Fechner in 1876. Edward B. Titchener also documented the effect and described the "glow of warmth" felt in the presence of something that is familiar. However, Titchener's hypothesis was thrown out once tested and 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 who is 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 by all organisms. Each repeated exposure to the novel stimulus causes less fear and more of an approach tactic by 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.
Zajonc (1960s) 
In the 1960s, a series of laboratory experiments by Robert Zajonc demonstrated that simply exposing subjects to a familiar stimulus led them to rate it more positively than other, similar stimuli which had not been presented. In the beginning of his research, Zajonc looked at language and the frequency of words used. He found that overall positive words received more usage than their negative counterparts.
One experiment that was conducted to test the mere-exposure effect used fertile chicken eggs for the test subjects. Tones of two different frequencies were played to different groups of chicks while they were still unhatched. Once hatched, each tone was played to both groups of chicks. Each set of chicks consistently chose the tone prenatally played to it. Zajonc tested the mere-exposure effect by using meaningless Chinese characters on two groups of individuals. The individuals were then told that these symbols represented adjectives and were asked to rate whether the symbols held positive or negative connotations. The symbols that had been previously seen by the test subjects were consistently rated more positively than those unseen. After this experiment, the group with repeated exposure to certain characters reported being in better moods and felt more positive than those who did not receive repeated exposure.
In one variation, subjects were shown an image on a tachistoscope for a very brief duration that could not be perceived consciously. This subliminal exposure produced the same effect, though it is important to note that subliminal effects are unlikely to occur without controlled laboratory conditions.
According to Zajonc, the mere-exposure effect is capable of taking place without conscious cognition, and that "preferences need no inferences". This statement by Zajonc has spurred much research in the relationship between cognition and affect. Zajonc explains that if preferences (or attitudes) were merely based upon information units with affect attached to them, then persuasion would be fairly simple. He argues that this is not the case: such simple persuasion tactics have failed miserably. Zajonc states that affective responses to stimuli happen much more quickly than cognitive responses, and that these responses are often made with much more confidence. He states that thought (cognition) and feeling (affect) are distinct, and that cognitions are not free from affect, nor is affect free of cognition. Zajonc states, "...the form of experience that we came to call feeling accompanies all cognitions, that it arises early in the process of registration and retrieval, albeit weakly and vaguely, and that it derives from a parallel, separate, and partly independent system in the organism."
In regards to the mere-exposure effect and decision making, Zajonc states that there has been no empirical proof that cognition precedes any form of decision making. While this is a common assumption, Zajonc argues that the opposite is more likely: decisions are made with little to no cognitive process. He equates deciding upon something with liking it, meaning that more often we cognize reasons to rationalize a decision instead of deciding upon it. Being that as it may, once we have decided that we 'like' something it is very difficult to sway that opinion. We are experts on ourselves, we know what we like, whether or not we have made cognitions to back it up.
Goetzinger (1968) 
Charles Goetzinger conducted an experiment using the mere-exposure effect on his class at Oregon State University. Goetzinger had a student come to class in a large black bag with only his feet visible. The black bag sat on a table in the back of the classroom. Goetzinger's experiment was to observe if the students would treat the black bag in accordance to Zajonc's mere-exposure effect. His hypothesis was confirmed. The students in the class first treated the black bag with hostility, which over time turned into curiosity, and eventually friendship. This experiment confirms Zajonc's mere-exposure effect, by simply presenting the black bag over and over again to the students their attitudes were changed, or as Zajonc states "mere repeated exposure of the individual to a stimulus is a sufficient condition for the enhancement of his attitude toward it".
Bornstein (1989) 
A meta-analysis of 208 experiments found that the mere-exposure effect is robust and reliable, with an effect size of r=0.26. This analysis found that the effect is strongest when unfamiliar stimuli are presented briefly. Mere exposure typically reaches its maximum effect within 10–20 presentations, and some studies even show that liking may decline after a longer series of exposures. For example, people generally like a song more after they have heard it a few times, but many repetitions can reduce this preference. A delay between exposure and the measurement of liking actually tends to increase the strength of the effect. The effect is weaker on children, and for drawings and paintings as compared to other types of stimuli. One social psychology experiment showed that exposure to people we initially dislike makes us dislike them even more.
Zola-Morgan (2001) 
In support of Zajonc's claim that affect does not need cognition to occur, Zola-Morgan conducted experiments on monkeys with lesions to the amygdala (the brain structure that is responsive to affective stimuli). In his experiments Zola-Morgan proved that lesions to the amygdala impair affective functioning, but not cognitive processes. However, lesions in the hippocampus (the brain structure responsible for memory) impair cognitive functions but leave emotional responses fully functional.
Two-factor theory 
The mere-exposure effect has been explained by a two-factor theory that posits that repeated exposure of a stimulus increases perceptual fluency which is the ease with which a stimulus can be processed. Perceptual fluency, in turn, increases positive affect Studies showed that repeated exposure increases perceptual fluency, confirming the first part of the two-factor theory. Later studies observed that perceptual fluency is affectively positive, confirming the second part of the fluency account of the mere-exposure effect.
The most obvious application of the mere-exposure effect is found in advertising, but research has been mixed as to its effectiveness at enhancing consumer attitudes toward particular companies and products. One study tested the mere-exposure effect with banner ads seen on a computer screen. The study was conducted on college-aged students who were asked to read an article on the computer while banner ads flashed at the top of the screen. The results showed that each group exposed to the "test" banner rated the ad more favorably than other ads shown less frequently or not at all. This research bolsters the evidence for the mere-exposure effect.
A different study showed that higher levels of media exposure are associated with lower reputations for companies, even when the mere exposure is mostly positive. A subsequent review of the research concluded that exposure leads to ambivalence because it brings about a large number of associations, which tend to be both favorable and unfavorable. Exposure is most likely to be helpful when a company or product is new and unfamiliar to consumers. An 'optimal' level of exposure to an advertisement may or may not exist. In a third study, experimenters primed consumers with affective motives. One group of thirsty consumers were primed with a happy face before being offered a beverage, while a second group was primed with an unpleasant face. The group primed with the happy face bought more beverages, and were also willing to pay more for the beverage than their unhappy counterparts. This study bolsters Zajonc's claim that choices are not in need of cognition. Buyers often choose what they 'like' instead of what they have substantially cognized.
In the advertising world, the mere-exposure effect suggests that consumers need not cognize advertisements: the simple repetition is enough to make a 'memory trace' in the consumer's mind and unconsciously affect their consuming behavior. One scholar explains this relationship as follows: "The approach tendencies created by mere exposure may be preattitudinal in the sense that they do not require the type of deliberate processing that is required to form brand attitude."
Other areas 
The mere-exposure effect exists in most areas of human decision making. For example, many stock traders tend to invest in securities of domestic companies merely because they are more familiar with them despite the fact that international markets offer similar or even better alternatives. The mere-exposure effect also distorts the results of journal ranking surveys; those academics who previously published or completed reviews for a particular academic journal rate it dramatically higher than those who did not. There are mixed results on the question of whether mere exposure can promote good relations between different social groups. When groups already have negative attitudes to each other, further exposure can increase hostility. A statistical analysis of voting patterns found that a candidate's exposure has a strong effect on the number of votes they receive, distinct from the popularity of the policies. Another example would be an automotive journalist claiming his own car being the best car in the world despite having driven countless cars.
See also 
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- Titchener, E.B. (1910). Textbook of psychology. New York: Macmillan.
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- Zajonc, R.B. (February). "Feeling and thinking: Preferences need no inferences". American Psychologist 35 (2): 151–175.
- Bornstein, R.F. (1989) Exposure and affect: overview and meta-analysis of research, 1968–1987. Psychological Bulletin, 106, 265–289.
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