Animal trainers who work in film and TV must teach the animal performer to behavior that they normally would not do; e.g., open a refrigerator and retrieve a beer. Simply reinforcing this behavior when it occurs will not work because...it will never occur. Therefore, these trainers use a technique known as ____________. That is, they reinforcer a series of approximations (e.g., approaching the refrigerator) that are successively closer to the terminal desired behavior. In the hands of a skilled trainer, it works every time.

acting

tugging

shaping

inducing