I've seen the term "cognitive artifact" or "cognitive tool" used before, in the sense of a technique or trick that, once known, transforms a person's abilities and even ability to think. It tends to permeate everything. Arithmetic is an example. Looking at the terrain and being able to abstract that to a map, whether mental or in the dirt/on paper, is another example. "Categorization" is probably one - putting things into abstract classes and sticking a label on them. Artifact is an interesting choice of word for it; human-made and passed like a material object. Yet children tend to learn them so young, we can't imagine how we thought before we knew them.
Written language, I think, is clearly in this category. Humans have had the physiology necessary for reading/writing for tens if not hundreds of thousands of years. And yet we did not write. In recent history, individuals from non-literate societies simply exposed, without intimate detail, to the idea of writing, have gone and invented their own writing system shortly after. (The Cherokee alphabet is probably such a development.)
What if spoken and sign language are like that? In discussions of the origins of human language, it is often framed as if an individual acquired a genetic mutation that allowed modern language usage and so they started speaking. But what if humans had the physiology necessary for a long time, but only made limited vocalizations, until someone or some group made the necessary mental leap, and so developed the process of abstraction and seemingly-infinite recursion that language allows? What if they successfully communicated it to others, and every human alive now is, in effect, culturally and mentally descended from them and their insight, unable to escape it even if we wanted to?