Answer:
spontaneous recovery.
Explanation:
So, let us first fill in the gap in the question above. Note that the capitalized words are the missing words in the gap..
"In his experiments, Pavlov found that SPONTANEOUS RECOVERY often occurred after a conditioned response was extinguished if the tone was presented again after a few hours without the CS or the US''.
Ivan Petrovich Pavlov was a great physiologist during his days and he is regarded as the Founder of modern behavior therapy.
Ivan Petrovich Pavlov was born in Russia on the 26th day of September, in the year 1849 and he died on 27th day of February, in the year 1936. In one of his experiment regarding conditioning, Ivan Petrovich Pavlov make use of dogs and he observed how dogs salivate before they are being giving food.
Just like it is given in the question, spontaneous recovery '' often occurred after a conditioned response was extinguished if the tone was presented again after a few hours without the CS or the US''.
SPONTANEOUS RECOVERY simply means that I taught a pet of mine something (let us say) A, and later I taught my pet another thing, say B. So, my pet forgets the first thing I conditioned it to(that is A) and only remembers something, B. Then, after sometime my pet started doing what I conditioned it to do in the first place (that is A) instead of B. That is called a spontaneous recovery!