Academic motivation has been associated with important outcomes in different education contexts. The goal of the current study was to explore the psychometric properties of the Academic Motivation Scale (AMS) based on the assumptions of the Rating Scale Model (RSM) to provide an effective instrument in assessing academic motivation in Portuguese students. The sample comprised 360 Portuguese university students that were assessed with the AMS adapted for online data collection. The results showed that the original version of the AMS with sevencategory response scale might not work properly with Portuguese university students. Different alternatives were tested by collapsing anchors in the endpoints and midpoint of the original response scale. This analysis revealed that the most suitable solution relies on a five-category response system with midpoint anchors collapsed. This final solution showed good overall fit according to the guidelines proposed for the RSM.: Education, Rating Scale Model, Item Response Theory, Motivation

Education, Rating Scale Model, Item Response Theory, Motivation