Salivary glands of a dog outperform its brain?

It is probably referring to Pavlov's dog experiments in the early 1900s.
http://www.simplypsychology.org/pavlov.html

Thanks.
What does "outperform its brain" mean then? "(His learnt response or his instinctive reaction) surpasses his reason"? Or be frank: :"he has no brain in doing so"?

Question remains.

It is impossible to give additional meaning without further context.

Perhaps Pavlov's experiments resulted in much more rapid learning, as measured by the experiments, than learning rates involving only the dog's brain. But that doesn't not make much sense. The activation of the salivary glands were a response mechanism. The experiments associated a stimulus (a light, a shape, a noise)

It simply means that its salivary glands worked better than its brain - i.e. a dog's level of biological functioning is better than its level of intelligence.