Foot-in-the-door (FITD) technique is a compliance tactic that involves getting a person to agree to a large request by first setting them up by having that person agree to a modest request. The foot-in-the-door technique succeeds owing to a basic human reality that social scientists call “successive approximations”. Essentially, the more a subject goes along with small requests or commitments, the more likely that subject is to continue in a desired direction of attitude or behavioral change and feel obligated to go along with larger requests. FITD works by first getting a small “yes” and then getting an even bigger “yes”.
The principle involved is that a small agreement creates a bond between the requester and the requestee. Even though the requestee may only have agreed to a trivial request out of politeness, this forms a bond which – when the requestee attempts to justify the decision to themselves – may be mistaken for a genuine affinity with the requester, or an interest in the subject of the request. When a future request is made, the requestee will feel obliged to act consistently with the earlier one.