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Abstract
The present study provides a comprehensive discussion on unfolding response processes with item response theory (IRT). Unfolding models reflect response processes with single-peaked response functions in contrast to cumulative response functions. The basic assumption is that a person will select items that are close to their location on the continuum. The study presents three studies. The first study provides a didactic description of unfolding models from a historical perspective. The second study presents a methodology-centered study, which introduces a conceptual framework for combining nonparametric and parametric unfolding IRT models. The third study provides an application-centered investigation, which describes an application of one of the unfolding models – Hyperbolic Cosine Model (HCM) to support formative assessment in student writing. This study endeavors to deepen our understanding of unfolding models, their applicability in attitude measurement, and their impact on educational assessment.