“The TOPRA model (Barcroft, 2000, 2002, 2003) was designed to represent visually how different types of processing can produce different types of learning outcomes. Three versions of the model appear in [figure below]. In each version, the thick outer lines remain stable because they represent the restricted amount of processing resources available to a learner. The inside lines can move, however, as different types of processing and corresponding types of learning increase or decrease, the basic idea being that each type of processing must exhaust processing resources. As one type of processing increases due to a specific type of task demand, others must decrease to accommodate. The amount and type of learning that ultimately takes place will reflect this kind of trade-off (see Barcroft, 2002, for discussion of TOPRA in light of levels of processing [Craik & Lockhart, 1972] and transfer-appropriate processing [Morris, Bransford, & Franks, 1977]).
The TOPRA model can be used to focus on how different types of processing should affect learning rates for distinct components of word knowledge, such as word form, word meaning, and form–meaning mapping. Whereas Version A (see Figure 2.1) is the general version of the model, Version B focuses on processing for word meaning, word form, and form–meaning mapping, and Version C focuses specifically on the semantic and formal components of word learning for contexts in which these two components are in play. Version C demonstrates most clearly the prediction that (when processing demands are sufficiently high) increased semantic processing can increase learning for the semantic (and conceptual) properties of words while decreasing learning for their formal properties. Word form learning decreases under these conditions because fewer processing resources remain available to process for word form.”
Barcroft, J. (2012). Input-based incremental vocabulary instruction. TESOL International
