What is the Foot-in-the-door technique?
The foot-in-the-door technique is the idea that it is more effective to start by asking people for something small, and then when they give it to you, you are in a better position to ask for something bigger.
Studies have shown that a small agreement creates a bond between the requester and the requestee. The person you ask acts according to the cognitive bias that they have to justify their agreement to themselves. Humans like to justify their decision-making so they will convince themselves that they accepted the first request for a reason and then feel obliged to act consistently with this reason by accepting a second and third request, and so on.
The phrase “foot in the door” originated during the heyday of door-to-door salespersons that would place their foot in the way of a closing door. With their foot literally in the door, the potential customer would have to listen to the sales pitch and this would potentially give them their way in to a bigger sale.