Answer:
This idea is according to the Opponent-Process Theory.
Explanation:
Opponent-Process Theory suggests the way an individual perceives colors is controlled by 3 opposing systems:
An individual can only detect one of the two colors from each system at a time, since once of the colors tends to conceal the other.
This theory can be applied to emotions as well, also looking at them as pairs of opposites such as:
In this case, once the stimulus which has caused fear ends, the opposite emotion will occur; relief.
