Reference of "it"

Salaam

What does "it" (underlined) in the the following paragraph refer to? Does it refer to "artificial intelligence" or it refers to "reinforcement learning" please?

At the time, neuroscientists had yet to figure out the mechanisms within the brain that allow animals to learn in this way. But Minsky was still able to loosely mimic the behavior, thereby advancing artificial intelligence. Several decades later, as reinforcement learning continued to mature, it in turn helped the field of neuroscience discover those mechanisms, feeding into a virtuous cycle of advancement between the two fields. (Source)