Hedonic Adaptation
Hedonic adaptation is the drift of satisfaction back towards its own baseline after a change in circumstances, upwards or downwards. Brickman and Campbell named the mechanism the hedonic treadmill in 1971, and the lottery-winner study everyone quotes came seven years later. Nir Eyal calls it Mother Nature's bait-and-switch and treats it as one of four reasons dissatisfaction is the human default. The strong version, that everyone returns to the same neutral point, was revised by wellbeing researchers in 2006 and does not hold.
What it is
Good things wear off. So do bad ones, more slowly and less completely, and the asymmetry is where the interesting part of this concept lives.
Philip Brickman and Donald Campbell set out the idea in "Hedonic relativism and planning the good society", a chapter in M. H. Appley's Adaptation-Level Theory symposium volume in 1971. Their argument borrowed Harry Helson's adaptation-level theory, in which the perception of any stimulus depends on the stimuli that came before it, and applied it to satisfaction. If your sense of how good today is depends on how good the recent past was, then improving the recent past also raises the bar you are measuring against, and the improvement cancels itself. They called the resulting arrangement a treadmill, and the metaphor has outlived almost everything else about the chapter.
Seven years later Brickman, Coates and Janoff-Bulman published the study that made it famous: "Lottery winners and accident victims: is happiness relative?", Journal of Personality and Social Psychology, 1978. Twenty-two major lottery winners, twenty-two controls and twenty-nine people paralysed in accidents. The winners were not happier than the controls, and reported taking significantly less pleasure from ordinary events than the controls did, which is the finding that actually deserves the attention and rarely gets it. The treadmill was not that winning failed to make them happy. It was that winning appeared to spoil the small things.
The strong claim built on this, that everyone returns to a shared neutral baseline and that efforts to raise wellbeing are therefore pointless, did not survive. Ed Diener, Richard Lucas and Christie Napa Scollon set out five revisions in American Psychologist in 2006, under the title "Beyond the hedonic treadmill". Baselines are not hedonically neutral, most people sit above neutral. Baselines differ between people and are partly temperamental. One person can hold several, since pleasant affect, unpleasant affect and life satisfaction can move in different directions at once. Baselines can change. And people vary widely in how fast and how completely they adapt to the same event. What is left after those five revisions is still a real phenomenon and no longer a law.
Eyal's use of the concept in Indistractable is narrower and does not depend on any of that arithmetic. He lists it as one of four mechanisms, alongside boredom, negativity bias and rumination, that between them keep satisfaction temporary, and cites David Myers's The Pursuit of Happiness for the observation that every desirable experience is transitory: passionate love, a spiritual high, a new possession, the exhilaration of success. His conclusion is the useful half. If satisfaction were permanent, striving would stop, so a nervous system that resets is functioning rather than failing, and the restlessness a person feels is a normal output rather than evidence of a defect. That is an argument. It is not a finding, and this page does not present it as one.