Answer:
a. An increase in his attempts to communicate with her.
Explanation:
The term extinction refers to a behavioural phenomenon that takes place in operant and classical conditioning. This describes the fading of non-reinforced conditioned responses over time. This occurs when an operant behaviour that has been previously reinforced no longer produces reinforcing consequences, which leads to the behaviour gradually stopping. However, a side effect of extinction is the sudden and temporary increase in the response, such as in the case of Curtis.