The term comes from Brickman and Campbell's 1971 adaptation-level theory research: a major positive change produces a real but temporary mood boost that fades as the gain becomes the new normal. OpenAI president Greg Brockman applied it directly to AI model releases in an August 15, 2026 tweet reading only "hedonic treadmill of model expectations" — naming why each frontier launch briefly excites users before its capability becomes the assumed floor, resetting the bar for the next release.