Repeated exposure of something leads to a more positive feeling about it.
Zajonc conducted four experiments, each of which provided overwhelming to strong support for the hypothesis that mere repeated exposure of an individual to a stimulus object enhances his or her attitude toward it. For example, in experiment #3, subjects were shown nonsense symbols that resembled Chinese characters. Each character was shown from 0–25 times. The subjects were then asked to rate how they felt about each character.
Eleven out of twelve times, the character was liked better when it was in the high frequency category.
The mere exposure effect is well established at this point. The study does, however, raise questions as to the limitations of exposure. Does this work in all situations? At what point does exposure not help with positive feeling? Does it matter what the intervals are of the exposure?
The mere exposure effect is an example of how irrational we can be. In no way does mere exposure mean that something is more trustworthy or deserving of positive feelings. This idea explains attachments to both animate and inanimate objects, and why sometimes it is hard to throw things away. Fear not; this same irrational bias that has caused you to form attachments to things you no longer have also works to irrationally help you form new attachments!