In classical conditioning, people learn to respond to a neutral object or event (the conditioned stimulus or CS) in a new way when it is paired with an emotionally meaningful object or event (the unconditioned stimulus or UCS). For example, we may develop strong feelings about a particular song (CS) because we associate with an emotionally important time in our life (UCS), such as a romantic break up or great vacation. The new learned reaction is known as the conditioned response (CR).