Adaptation Level Theory
A theory proposed by the US psychologist Harry Helson (1898–1977) in an article in the American Journal of Psychology in 1947.
It refers to the theory that emotions and sensations are relative and quick to change. Humans tend to adapt to their surroundings and no longer respond to the novelty of certain stimuli after a period of time has passed. The phenomenon can manifest itself in a need for more and more stimuli to create the same effect; for example, someone addicted to gambling or high-speed racing needs more of a thrill each time to experience the same level of happiness.