Backward Conditioning (Backward Pairing)
Backward conditioning (also known as backward pairing) is a behavior conditioning method in which the unconditioned stimulus (US) is presented before a neutral stimulus (NS). This is a mostly ineffective method of conditioning because it doesn't allow for a clear association between the US and the NS.
The NS is what you want to become a conditioned stimulus (CS).
So to use a Pavlovian example, an experimenter rings a bell (NS) before they present the food (UCS). Eventually the bell will cause salivation without the presentation of food which is when it becomes a CS. In backward conditioning, the US (food) is presented to a dog before the NS (a bell). Therefore, the dog does not associate the bell with food and the NS will not become a CS and cause salivation on its own.