Simply being exposed to something repeatedly tends to make people like it more.

The mere-exposure effect describes a robust and well-replicated finding: repeated exposure to a stimulus, whether it’s a song, a face, a shape, or even a nonsense word, tends to increase how much people like it, even when they aren’t consciously aware they’ve encountered it before. Psychologist Robert Zajonc demonstrated the effect experimentally in the late 1960s, and it has since been confirmed across hundreds of studies with images, sounds, and even people.

The effect helps explain everyday phenomena like why songs often grow on people after a few listens, why advertisers value repeated exposure over a single impression, and why familiar faces tend to be rated as more trustworthy and likable than unfamiliar ones. It typically has diminishing returns and can even reverse into irritation with excessive repetition, but at moderate levels, familiarity reliably breeds fondness rather than contempt.