Our brain prefers visually, things that are already familiar (mere exposure), things that are repeated over time. We like also superstimuli (exaggerated stimuli), evolutionary stimuli like faces or features of a face. We prefer also symmetry like Golder Ratio, symmetry, proximity, similarity, continuity, closure. (Gestalt properties).
For example, we prefer shapes that are rounded and not sharp for products, because they make us feel in danger, and in another hand the rounded make us feel safe.
What we can learn as designers?
In web/ui design we can use rounded shapes to convey more safe feeling for the user, this will increase the likability of the design. To change likability, we can also use mere exposure by exposing the user to the same stimuli over time, and keeping something constant. Repeated stimuli cause activation in the reward system. Repeated exposure of a stimulus increases perceptual fluency which is the ease with which a stimulus can be processed.