Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: In an experiment, a scientist named Pavlov rang a bell before he fed his dogs, which made the dogs drool. Soon the dogs would drool when they heard the bell, even if they did not receive any food. What type of response did the dogs exhibit?
a learned behavior
Classical conditioned response.