developed by Stephen Krashen). Instruction must include extensive L2 input. Instruction must include opportunities for output. Interaction with the language is the basis of proficiency-building. Instruction must consider the individual differences of learners. Assessment should include both free and controlled production. The basis for this list is grounded in various theoretical perspectives, though namely the computational model of L2 learning developed by James Lantolf. This model has its limitations according to Ellis, as it does not account for social relations and contexts. However, it provides an appropriate basis for establishing a set of principles for language instruction. Form-Focused Instruction versus Meaning-Focused Instruction Ellis maintains that the distinction between form-focused instruction and meaning-focused instruction lies in how language is perceived and the role of the student. The former is concerned with drawing the student's attention to linguistic form (including, but not restricted to, vocabulary and grammar) whereas the latter focuses on conveying messages. In taking note of the reconceptualization of focus-on-form by other scholars, notably Michael Long, Catherine Doughty and Jessica Williams, Ellis distinguishes between planned and incidental focus on form. According to Ellis, there are three types of form-focused instruction: Focus on forms: can be implicit or explicit, can include structured input or production practice and it can include functional language practice. Planned focus on form: can include enriched input or a focused communicative task. Incidental focus on form: can be pre-emptive or reactive; can include implicit negative feedback or explicit negative feedback. The effectiveness of form-focused instruction depends on multiple variables, such as the linguistic items being taught, the learners' developmental stage, the instructional context and instructional materials. Ellis also maintains that form focused instruction not only facilitates language learning, but also that it does not change the sequence of language development. Corrective Feedback In a 2006 study, Ellis found that groups of students who had been given explicit instructions and grammar rules prior to taking multiple tests at different times initially had different outcomes based on what was being assessed, but by the final test, there was little to no difference between the groups of students. In the same study, Ellis argues that students may already possess certain knowledge of a language's grammar, but when shown how to use this internal knowledge correctly, the acquisition of the language can dramatically increase. Ellis argues in favour of explicit feedback rather than implicit feedback, such as recasts. Accordingly, with the