Answer: The inactive lever or nose poke hole serves as a control measure of activity.
From: https://www.hindawi.com/archive/2014/209875/fig3/
A self-administration drug delivery behavioral test can be done in order to assess an organism’s desire to obtain a drug. The animal is implanted with an indwelling intravenous tube that can deliver drug directly into the bloodstream. The animal is placed into a responding chamber which may have two interactive components. These may either be levers which protrude into the chamber, or holes into which the animal may poke their nose.
Of these two components, one of them is an “active” and the other is “inactive.” A response on the active lever will give the animal an infusion of drug. Pressing the inactive lever does not deliver drug.
The inactive lever serves as a control. If an animal were bored, they might press the lever on the wall to relieve the boredom. If so, then the experimenter is not actually measuring drug seeking behavior any time a lever is pressed.
