The drift back toward a baseline level of happiness after good or bad events — named the hedonic treadmill because you keep walking and stay in place.
Philip Brickman and Donald T. Campbell, 1971.
// Where it sits
Slightly toward adaptation, and nowhere near the absolute version people repeat.
What it really means
You have heard this study. It is one of the most-cited findings in popular psychology, and the version you have heard is wrong.
The claim, as it circulates: lottery winners and people paralysed in accidents end up about equally happy. Therefore nothing durably changes your happiness, therefore the pursuit of circumstances is futile.
Here are the actual numbers from the 1978 paper, on a 0–5 present-happiness scale:
Lottery winners: 4.00. Controls: 3.82. Accident victims: 2.96.
The accident victims were significantly less happy than the controls. That is not a null result. That is a clear difference, in the direction anyone would expect, and it is in the paper.
The genuine null was between the 22 winners and the 22 controls — winning a lottery did not make people meaningfully happier. That finding is real, interesting, and has been quietly extended to a claim the data never supported.
The winners' most striking result is subtler and rarely quoted: they rated everyday pleasures lower — 3.33 against the controls' 3.82. Not miserable. Less delighted by small things, which is a specific and slightly sad cost.
The underlying idea, the hedonic treadmill, was named in 1971 by Brickman and Campbell — and the image is theirs, not a later popularisation. You walk; you stay where you are.
But the strong version of the theory has also been revised by its own field. A 2006 review by Diener, Lucas and Scollon set out five corrections, and the important one is this: set points are not fixed. Longitudinal work shows lasting shifts in baseline wellbeing after widowhood, unemployment, divorce and disability. Some events do not get adapted away.
So the honest summary is narrower than either version you usually meet. Adaptation is real and powerful. It is not total, it is not universal, and the study everyone cites to prove that circumstances don't matter is a study in which circumstances mattered.
This page is educational and not a diagnosis.
Where it comes from
The load-bearing image, TREADMILL, is Brickman and Campbell's own from 1971 — not a later popularisation. The root glosses are standard reference knowledge rather than verified for this page.
Myths & misconceptions
The 1978 study showed lottery winners and paralysed accident victims end up equally happy.
It showed nothing of the kind. On the 0–5 present-happiness scale: winners 4.00, controls 3.82, accident victims 2.96. The accident victims rated themselves SIGNIFICANTLY LESS HAPPY than controls. The genuine null result was between the 22 winners and the 22 controls — never between victims and controls.
Everyone returns to a fixed happiness set point.
A 2006 revision by Diener, Lucas and Scollon lists five corrections to the theory, including that set points are NOT fixed. Longitudinal evidence shows lasting shifts following widowhood, unemployment, divorce and disability — the baseline itself moves.
Compare & contrast
Hedonic adaptation vs set-point theory
Set-point theory is the strong claim — a fixed baseline you always return to. Hedonic adaptation is the weaker observed process. The 2006 revisions kept the process and abandoned the fixed point.
| // | Hedonic adaptation | Set-point theory |
|---|---|---|
| Claims a fixed baseline | No | Yes |
| Survived review | Yes | Not intact |
| Applies to everyone equally | No | Claimed yes |
| Status | Process | Revised |
How it connects
- Gratitudethe intervention most often proposed against it, with its own weak evidence.
- Flourishingthe outcome measure this whole literature is arguing about.
Tell it apart
Questions people ask
- Did lottery winners end up unhappy?
- No. They were not significantly happier than controls, and they rated everyday pleasures lower — 3.33 against controls' 3.82. 'Less delighted by small things' is the finding, not 'miserable'.
- So the paralysed participants were just as happy?
- No, and this is the single most repeated misreport in happiness research. They scored 2.96 against controls' 3.82 — significantly less happy. The claim that serious injury makes no lasting difference is not what the study found.
- Does adaptation always win?
- No. Longitudinal work shows some events — widowhood, unemployment, disability — shift the baseline durably rather than being adapted away. This page is educational and not a diagnosis.