Fischer's developmental web

From this piece:

"Skills are constructed over time, and as Dr. Fischer's research has shown, variability in skill performance is normal. Development is not like climbing a ladder, where each step up equates to the perfect achievement of a new set of skills. Instead, development is like a spider's web, with growth in change through many pathways at once. Different skills can be at different levels of complexity at the same time. There can be differences across domains, where (for example) math skills might run ahead of social studies skills. Or there can be differences within domains, where multiplication skills might run ahead of division skills. There is also variability within a single skill. Students may demonstrate a skill in one context, and fail to do so in another. A period of building skill followed by regression is also normal. When students are building a new skill or concept, they are likely to 'forget' what they've learned a few times before the new skill can be taken for granted."