Backward pairing is a term in classical conditioning referring to the presentation of the unconditional stimulus (US or UCS) before the conditoned stimulus (CS). (see Delayed pairing, Trace pairing, Simultaneous pairing.)
This is the opposite of the more common forward pairing, where the CS is presented before the UCS.
Backward pairing is generally less effective in producing a conditioned response than forward pairing, and is not typically used in experimental research. However, it can occur naturally in certain situations, such as when a previously neutral stimulus becomes associated with a strong emotional response after the emotional response has already occurred.
An example of backward pairing could be a person feeling anxious or fearful after encountering a particular stimulus, and then later learning to associate that stimulus with their anxious or fearful response. In this case, the anxiety or fear response would be the UCS and the stimulus would be the CS. However, this type of conditioning is generally considered weaker than forward pairing, where the stimulus is presented before the emotional response.