i) Reinforcement: You know that you can elicit a conditioned response by the pairing of CS and UCS. Since UCS (meat powder) comes later than CS (bell), the presentation of CS alone elicits salivation. But you need to give the dog the UCS consistently after the bell. So here meat powder serves as the reinforcer, as it strengthens the bond between the CS and the UCR (salivation in this case).
ii) Extinction: What will happen if you do not reinforce the association between the CS and UCS? In other words, after conditioning is established, you sound the bell but do not reward the dog by giving meat powder? You will observe that after a few such trials with no reinforcer, the salivation still occurs, but in a decreased amount.
iii) Spontaneous recovery: Sometimes, after extinction, and after a time interval with no exposure to CS, the conditioned response may suddenly come back if the CS is given once again. The dog’s salivation to the bell has been stopped. The bell has also not been sounded for a considerable time. If after this gap the bell is suddenly sounded, the dog may start salivating once again.
iv) Stimulus generalisation: Will the dog salivate only in response to the sound of the specific bell or to the specific light? Will it respond by salivating to other bells as well? Pavlov conducted further experiments to examine these questions. He initially made a standard UCS-CS connection of food and a specific sound of a bell. On test trials, he substituted the original sound with other sounds varying in similarity.
v) Discrimination: This is the opposite of generalisation. You have learnt that generalisation occurs to stimuli similar to the CS. But if stimuli similar to the CS and eliciting the CR are presented repeatedly without ever being associated with the UCS, those stimuli will cease to elicit the CR, thus enabling discrimination between similar stimuli.
vi) Counter conditioning: Once conditioned, ever conditioned? Of course not. As you can extinct an acquired learning, you can also counter condition it by associating the CS with UCS of different nature. For example, you can first condition a dog to withdraw its paw at the sound of a bell, as the bell is systematically followed by a shock.