Priming is the demonstrated effect where exposure to one concept — even briefly, even without conscious awareness — measurably shifts behavior or judgment related to that concept afterward. This isn't a subtle statistical footnote; well-documented priming studies show people physically walking slower after unscrambling sentences containing old-age-related words, without any of them ever being told the study was about aging at all.
The unsettling implication is that behavior can be nudged by inputs a person never consciously registers as relevant, which is precisely what makes priming effects useful to understand defensively: environments (a waiting room, a checkout aisle, a meeting room) contain far more subtle behavioral cues than most people account for when explaining their own choices.
Psychologist John Bargh had NYU students unscramble sentences containing words associated with old age — 'Florida,' 'forgetful,' 'bald,' 'wrinkle' — without the word 'old' or 'aging' ever appearing directly, and without any mention that the study concerned aging at all. Afterward, researchers secretly timed how long it took each student to walk down the hallway to the elevator. Students who'd unscrambled the aging-related sentences walked measurably slower than students who'd unscrambled neutral sentences — an unconscious concept had produced a measurable physical change in behavior.