What does "its" refer to?

Hi~ In the following sentence underlined, I don't figure out what the word "its" refer to?

What do you think is the best reasoning? Instruction OR higher-level thinking?

Thanks for your help in advance~

Teachers often focus on producing higher-level thinking through traditional instruction. While teachers may recognize when higher-level thinking occurs with individual students, they don’t necessarily know how to
consciously increase its occurrence. The process of learning does spur on higher-level thinking but does not necessarily guarantee that it will happen. Therefore, many teachers often perceive that certain students
get it and others do not. Even more tragic is the fact that some educators believe that higher-level thinking is a level of understanding that is reserved for the more intellectually gifted students. Science has dispelled the
notion that higher-level thinking is correlated with intellect. The truth is that higher-level thinking is a natural occurrence of the human brain. It is the brain making connections to prior knowledge producing deeper levels of
comprehension.

What methods of instruction increase the occurrence of higher-level thinking to boost its production? The first crucial requirement for higher-level thinking is automation. Higher-level thinking requires that fundamental knowledge be retrieved quickly. With each repetition, the brain does not have to expend such high energy recognizing, comprehending, and recalling. Automation allows for other cognitive processes to occur, creating more advanced associations.