Final answer:
The rats used cognitive maps to navigate through the maze and find the route out of NIMH. They did not take anything physical into the air duct to help them.
Step-by-step explanation:
In the book 'Mrs. Frisby and the Rats of NIMH' by Robert C. O'Brien, the rats used cognitive maps to navigate through the maze. They did not take anything physical into the air duct to help them find the route out of NIMH. Instead, they relied on their mental representation of the maze to guide them.
This type of learning, known as cognitive learning, was demonstrated in experiments conducted by psychologists Edward Tolman and H.C. Blodgett. They found that rats develop a cognitive map of the maze and use it to navigate, even without a reward or reinforcement.