Pavlov taught a dog to salivate at the sound of a musical tone by repeatedly pairing the tone with food. in this example, the musical tone is the before conditioning and the after conditioning.

The answer is neutral stimulus; conditioned stimulus. A neutral stimulus is a spur which originally makes no exact answer except concentrating responsiveness. In classical conditioning, when put together with an unconditioned stimulus, the neutral stimulus turn out to be a conditioned stimulus.

answer; basic psychology;