The concentric approach, often called spiral, is a way of organizing a curriculum by laying out basic concepts, covering other related material, and then circling back around to the basic concept and filling in more complexity and depth. It differs from the topical approach, in which all relevant material is covered in linear fashion and concepts are not revisited, and the functional approach, which emphasizes skill building and avoids theoretical background.

Arithmetic and mathematics have been taught using concentric methods for many decades. Numbers are introduced and studied, revisited as addition is added, revisited again with subtraction, multiplication and so on. Another example is the teaching of science in Chinese schools: Instead of life science, earth science, physics, biology and chemistry being separated and studied in sequence, each year's curriculum revisits the sciences studied earlier. It's believed that starting with fundamentals that are then regularly revisited, built on, deepened and broadened each time leads to a better understanding of a subject's interconnections.

The concept of concentric curriculum design is based on the cognitive psychological theories of Jerome Bruner. Bruner believed that there are three distinct stages in the human cognitive process: the enactive phase, in which the learner interacts with and uses objects or processes; the iconic phase, in which the learner manipulates images of these objects or processes; and the symbolic phase, in which abstract representations of them can be utilized. Concentric curriculum design attempts to leverage this understanding of cognition into a deeper understanding of the subject at hand.

Theorists and curriculum designers at the Active Learning Practices for Schools online community set up by Harvard University's Graduate School of Education and Project Zero have diagrammed a "Learning Spiral" template designed to help educators apply concentric theory to their curricular design. The template suggests a five-phase analysis -- learning by getting ready, learning from sources, learning by doing, learning from feedback and learning by thinking ahead -- that helps generate "thinking-centered lessons."

Researchers have found it difficult to demonstrate empirical results that prove that the concentric approach to a subject, as a whole, always leads to better learning outcomes. But some of its inherent principles and components, and the cognitive psychology supporting it, have been shown specifically to achieve better outcomes when broken into smaller bites, especially in writing and reading and technical studies. It is possible that a concentric approach works better in some subjects than in others, or that it works better for some learners than for others.