Answer:
We should expect that the rat will have more difficulty learning the task than a regular rat.
Step-by-step explanation:
Dopamine plays various roles on the brain, such as enhancing the executive functions, playing a role on motivation, pleasure and gratification. It is the reward system, meaning that it plays a big role in getting an individual to do something because of the reward he/she gets from it, thus motivating the individual.
In this case, we can conclude that the rat with the blocked dopamine activity will have more difficulty learning the lever-pressing task because it loses its reward system and its motivation to do so.