There is a concept in social psychology known as the mere-exposure effect or the familiarity principle which states that people develop a preference for things that they perceive as familiar, even if there is no further reason to trust them.
The most well known research on the subject was conducted by a Polish-born American social psychologist by the name of Robert Zajonc in the 1960s who observed that exposure to a new or unfamiliar stimulus caused a fear/avoidance response in people while repeated exposure led to them becoming more comfortable with the stimulus and eventually liking showing preferences for it. He also found that the effect could be seen not only in humans but in a wide range of different organisms.
In many ways this could be seen as a rational response – fear of the unknown protects us from dangers for which we may be unprepared, but we develop familiarity to things far more easily than you might think. For example, the findings show that you are more likely to develop an affinity for a complete stranger that you occasionally see walking along the street than you are for a complete stranger than you have not.
Robert Bornstein discovered in 1989 that affinity for a stimulus is likely to develop more effectively if people are not aware of the stimulus. The effect was also shown to increase with the number of exposures, with the optimum effect being 10-20 exposures, after which preference can actually start to decrease.
This principle can be applied to your advertising campaign and shows the value in building familiarity with your brand over a period of time. The more people see your brand promoted, the more likely they are to feel an affinity towards it at the point where they would be about to buy your product or use your service. There’s also an implication that if you are promoting a new product, then there would be advantages in using familiar imagery or language (or at least types of imagery or language) in order to make people more comfortable with what you do.