“…The mixture IRT approach for polytomous items is widely applied in empirical social research, mainly with the purpose of exploring population heterogeneity and its causes. For example, mixture polytomous IRT models are useful for detecting latent classes that qualitatively differ in a measured personality trait or attitude (e.g., Egberink et al, 2010; Finch and Pierson, 2011; Baghaei and Carstensen, 2013; Gnaldi et al, 2016; Jensuttiwetchakul et al, 2016) or those that are characterized by response styles (e.g., Eid and Rauber, 2000; Austin et al, 2006; Wagner-Menghin, 2006; Eid and Zickar, 2007; Maij-de Meij et al, 2008; Meiser and Machunsky, 2008; Wu and Huang, 2010; Wetzel et al, 2013). Moreover, they can be applied to examine construct validity (e.g., von Davier and Yamamoto, 2007; Tietjens et al, 2012), to detect differential item functioning (e.g., Frick et al, 2015; Cho et al, 2016), and to check the quality of a rating scale in general (e.g., Smith et al, 2011; Kutscher et al, 2017).…”