【双语版】巴甫洛夫经典条件反射Pavlov Classical Conditioning
喂狗的过程中，在给肉（无条件刺激）前加入铃铛刺激（条件刺激），狗会逐渐习得二者之间的联系，从而在铃铛响起时也会流口水（条件反射）。
实验发现有三：
习得的速度取决于两点，一是刺激的明显与否; 二是条件刺激和无条件刺激（即铃声与给肉）的间隔时间，间隔时间越短，习得越快。
所习得的条件反射很容易消失，只响铃而不给肉几次后，狗就不会对响铃刺激分泌唾液。但当重新结合两个刺激时，这种习得又很容易重新出现。
习得可被泛化，即狗会对与铃声相似的刺激做出反应；狗也可学会区分刺激，只对正确的刺激产生反应。
When continuosly combine feeding (unconditioned stimulus, US) with a bell ringing (conditioned stimulus, CS), the dog would learn to salivate alone with the sound of the bell. It is called the learning of conditioned response (CR).
Pavlov's experienment found that
The rate of acquisition is dependent on the noticeability of the stimulus, and also the time between the neutral stimulus (aka the conditioned stimulus designed by the researcher, in this case, the bell ringing) and the unconditioned stimulus. The shorter the latter one is, the quicker the acquisition would be.
The conditioned response is vulnerable to extinctioin. Once the researcher stop to feed the dog and only ring bell, the dog would stop to salivate. But if the combination of US and CS appear again, the learing would recover.
There are generalization and discrimination for the stimulus learning. The dog would response to similar stimulus (e.g. ringtone on the phone) and was able to only react to the right stimulus once trained.
参考：
Classical Conditioning StatPearls [Internet], NCBI book shelf
