Definition
Commitment and consistency is the principle that, once we have taken a position — said something, signed something, done something — we feel a strong pressure to behave in ways consistent with that earlier position. The principle has two faces: commitment is the initial act, and consistency is the subsequent drive to maintain the behavior, belief, or stance that the commitment implied.
Cialdini's contribution in the Commitment-and-Consistency topic is to identify the four features that make a commitment durable: active (you said or did it, not just agreed silently), public (others saw or heard), effortful (you worked for it), and freely chosen (no obvious external pressure). A skilled compliance professional stacks as many of these as possible at the moment of the initial agreement.
Why it matters
How it works
The mechanism runs through self-perception. After agreeing to a small request, we infer that we are the kind of person who agrees to such requests. The inferred identity then writes new defaults for adjacent decisions — the next request is no longer evaluated freshly but against the prior identity. The commitment ratchet only turns one direction without conscious intervention.
This is why the foot-in-the-door technique works so reliably. A trivial first agreement (sign a petition, accept a small gift, agree in principle) updates the target's self-image. The second, much larger request is then evaluated by an already-committed self. The lawn-sign study (Freedman & Fraser, 1966): homeowners who first agreed to display a tiny "Be a Safe Driver" sticker were four times more likely to later agree to a giant ugly billboard in their yard than control homeowners who got the billboard ask cold.
The lowball technique uses the same principle in reverse: secure agreement at a favorable price, then "discover" the price was wrong. Most customers pay the new price because they have already mentally committed to owning the item.
The defense is to ask, at every transition: if I came into this situation fresh, with no prior commitment, would I make this choice today? If the answer changes when you imagine starting over, consistency is doing the work, not the merits.