Answer:
Foot-in-the-door technique.
Step-by-step explanation:
This method is commonly used in the field of social psychology. It is a type of compliance method. The basic principle is to ask someone for something small and modest and have them agree on that. If the request is accepted and the person who agreed feel an obligation to agree to a bigger request to stay consistent to the their first decision. This method is used to increase the likelihood of agreeing to your request. It is a reference to the door to door salesman who keeps the door from shuting with his foot.