CLASSICAL CONDITIONING SIGNIFICANCE - Characteristics
The response involved is essentially a pre-existing reflex, the learning which occurs does NOT involve a new response; instead it consists of forming a connection (association) between two stimuli (the CS and UCS). In order for optimal conditioning to occur the conditioned stimulus (CS) must occur a second or so before the unconditioned stimulus (UCS). If the two occur simultaneously, conditioning may occur, but is typically weaker. If the CS is presented AFTER the UCS, then NO learning occurs. What this tells me is that conditioning is closely linked to the ability of the CS to serve as a signal that the UCS is going to occur.