Contrast effect is a phenomenon in which the perception of one stimulus is affected by the presence of another. It is a cognitive bias in which an individual's perception of a given stimulus is influenced by the presence of another stimulus. This effect can be seen in a variety of contexts
From Wikipedia
A contrast effect is the enhancement or diminishment, relative to normal, of perception, cognition or related performance as a result of successive or simultaneous exposure to a stimulus of lesser or greater value in the same dimension.