Assessing functional adequacy in oral dialogic speech: Validating a rating scale for L2 interaction

Functional Adequacy (FA), a multidimensional construct emphasising successful task completion, has developed into an established line of research in second language acquisition (SLA). Kuiken and Vedder’s (2017, 2018) FA rating scale, which operationalises FA across four dimensions (Task Requirements, Content, Comprehensibility, Coherence & Cohesion), has been shown to provide a reliable and valid instrument for assessing second language (L2) performance in monologic tasks. Contrary to monologue performance, few studies have, however, investigated L2 interaction due to its inherent complexity (Galaczi & Taylor, 2020). Recent research has called for adaptations of the FA monologue scale for dialogic data (González-Lloret, 2022). To this end, Kuiken and Vedder (2025) substituted the Coherence & Cohesion dimension of the monologue scale with a new dimension, Interaction, focusing on the adequacy of speakers’ engagement in situated communicative interaction. Our study explores the reliability, validity, and applicability of the adapted FA scale for interactional speech. Through three pilot studies involving L2 learners of Italian and English with three groups of raters, three issues were addressed: the correlations of raters’ judgments on the Interaction dimension, the associations among the four FA dimensions, and the raters’ experiences and challenges in applying the adapted scale. The three pilots showed a largely sufficient to high interrater reliability for Interaction. Moderate to high correlations were found between Interaction and Task Requirements, Content, and Comprehensibility. The raters’ feedback confirmed the applicability of the scale and the relevance and clarity of the descriptors for assessing dialogic performance. With some caution, we may conclude that the adapted FA scale constitutes a promising instrument for assessing L2 oral interaction.