1) Respondent conditioning occurs when an organism responds to a new event based on a history of association with a biologically important stimulus. The Russian physiologist Ivan Pavlov discovered this form of conditioning at the turn of the century. He showed that dogs salivated when food was placed in their mouths. This relation between the food stimulus and salivation is called a reflex and occurs because of the animals' biological history. When Pavlov rang a bell just before feeding the dog, it began to salivate at the sound of the bell. In this way, new features (sound of bell) controlled the dog's respondent behaviour (salivation). Thus, presenting stimuli together in time (typically CS then US) is the procedure for respondent conditioning. If a CS comes to regulate the occurrence of a conditioned response (CR), respondent conditioning has occurred.

"2) The modification of respondent behaviour by stimulus-stimulus contingencies, also referred to as classical conditioning or Pavlovian conditioning.

3) A neutral stimulus acquires the eliciting properties of an unconditioned stimulus through pairing the unconditioned stimulus with a neutral stimulus. "

4) The establishment and strengthening of a conditioned reflex through the roughly simultaneous presentation of unconditioned and conditioned stimuli, as in the Pavlovian experiment.