The strength of associations can also be judged by the resistance to extinction - that is, how long an animal will keep responding in the presence of an SD whithout reiforcement. One of the main features of all schedules of reinforcement which are partial - that is where not every single response is reinforced, is that they produce learning which is much more resistant to extinction than continuous reinforcement.
In operant conditioning appetitive and aversive events produce different patterns of earning. One can distinguish between four different consequences of responding in operant conditioning:
Although animals can learn all of these contingencies it is very clear that they have quite different consequences in extinction. When a contingency fails to apply to a behavior actively produced by the animal it is clear that the contingency is not longer in operation. On the other hand, if behaving leads to aversive consequences then, in extinction the animal is unlikely to produce the behavior and hence to discover that the contingency no longer applies.