## Key Ideas > [!abstract] Core concepts > > - Break complex skills into components, practise each extensively before combining > - Prevents working memory overload by reducing interacting elements students must process simultaneously > - Coherent curriculum sequencing rather than individual lesson design ensures logical skill progression ## Definition **Part-whole approach**: Instructional design method that presents complex content in small, manageable steps with extensive practice after each step to chunk and automate knowledge before integration. ## Connected To [[Atomisation]] | [[Knowledge-Based Curriculum]] | [[Memory]] | [[Cognitive Load Theory]] | [[Explicit Teaching]] | [[Element Interactivity]] | [[Chunking]] | [[Practice]] --- ## Theoretical foundation Working memory can process only approximately four novel elements simultaneously (Cowan, 2001; Miller, 1956), so content should be presented in [[Atomisation|small, manageable steps]] that respect cognitive capacity. Each step should be [[Practice|practised]] extensively to [[Chunking|chunk]] and [[Fluency|automate]] the knowledge before adding complexity (Cooper & Sweller, 1987; Ericsson & Kintsch, 1995). This curriculum sequencing optimises [[Cognitive Load|intrinsic cognitive load]] by controlling the number of interacting elements students must process simultaneously (Sweller, van Merriënboer, & Paas, 2019). The part-whole approach, also known as the subgoal learning model, helps learners identify meaningful problem-solving steps and apply them to novel problems (Catrambone, 1998). When elements of a task have high interactivity and cannot be understood in isolation, they should be taught separately before integration (Pollock, Chandler, & Sweller, 2002). This approach is a key aspect of [[Explicit Teaching]], ensuring students master components before attempting integration (Rosenshine, 2012; Archer & Hughes, 2011). ## Planning and implementation A part-whole approach requires teachers to plan entire units of work to ensure coherence, rather than planning individual lessons in isolation. Skills and knowledge hierarchies make explicit the [[Element Interactivity|interacting elements]] that must be mastered before a student can achieve the intended goal. When planning a worked example, teachers should ask "What prerequisite skills are needed to have the best chance of learning the new method?" (Rosenshine, 2012). This question can be answered through supporting syllabus documents, textbook analysis, or by asking "What was done to go from this line to the next line?" (Catrambone, 1998). Implementation follows four phases. In the decomposition phase, teachers identify component skills whilst students learn individual elements. During the isolation phase, students practise each component separately to master discrete skills through targeted practice. In the integration phase, students apply skills together under teacher guidance. The automation phase develops fluency whilst students perform with minimal effort and teachers monitor and refine performance. ## Practice and performance Complex skills are made up of many different elements (Christodoulou, 2014). In marathon training, for instance, a practising marathon runner aims to travel 42km in shorter times, but effective segmentation does not simply mean practising that overall 42km in chunks. Runners also practise other exercises, such as body weight exercises, stretches, and weight training, that support the final performance in diverse ways. Practice looks different to the final performance because component skills require targeted development before integration. In teaching algebraic fractions, students need automated mastery of basic fraction operations, factorisation, finding LCM, and simplification before combining these in complex problems. For essay writing, students master paragraph structure, topic sentences, evidence selection, and analysis separately before writing complete essays. When solving quadratic equations, students automate expanding brackets, factorisation patterns, and solving linear equations before tackling quadratics. ## Common difficulties Students often cannot combine component skills without explicit instruction (Pollock et al., 2002). Insufficient practice at component level leads to cognitive overload during integration (Sweller et al., 2019). Teachers who skip hierarchy analysis miss prerequisite skills (Rosenshine, 2012), and individual lesson planning ignores coherent skill progression across units. ## References Archer, A. L., & Hughes, C. A. (2011). *Explicit instruction: Effective and efficient teaching*. 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