An operational definition of the emergence criterion

Although acquisition criteria are a fundamental issue for SLA research, they have not always been adequately defined or elaborated in the literature. This article critically scrutinizes one such criterion, the emergence criterion, proposing an explicit, operational definition. After discussing emergence as a theoretical construct, the article addresses several points involved in its operationalization. These points concern all stages of a research project, from data collection to data organization and analysis. A concrete example is provided, leading to the formulation of an emergence criterion for the acquisition of two grammatical structures of Italian as a second language. Issues of reliability and validity are also discussed, providing indications for future research.