Mere exposure effect

Exposure effect is a psychological artifact well known to advertisers: people express undue liking for things merely because they are familiar with them. This effect has been nicknamed the "familiarity breeds liking" effect.

Simply exposing experimental subjects to a picture or a piece of music briefly led those subjects to later rate it more positively than other, similar stimuli which they had merely not been shown earlier. In another experiment, students were shown a Chinese character on a tachistoscope faster than could be perceived consciously. Later, students rated these characters as better than those to which they had not been exposed. When asked, the students were able to cite specific and detailed reasons why they preferred the characters that they did (which must have been at least partially rationalization).

The effect might be explained by the idea that recognizing a familiar environment makes us feel safe. This effect was first studied by Robert Zajonc. A related effect relevant to advertising and propaganda is the sleeper effect.