Compare methods

	Social Identity Political Measurement	Affective Polarization Measurement
Field	Political Psychology	Political Psychology
Family	Process / pipeline	Process / pipeline
Year of origin	2015	2012
Originator	Leonie Huddy, Lilliana Mason & Lene Aaroe	Shanto Iyengar, Gaurav Sood & Yphtach Lelkes
Type	Self-report identity scale	Composite survey index
Seminal source	Huddy, L., Mason, L., & Aaroe, L. (2015). Expressive partisanship: Campaign involvement, political emotion, and partisan identity. American Political Science Review, 109(1), 1-17.	Iyengar, S., Sood, G., & Lelkes, Y. (2012). Affect, not ideology: A social identity perspective on polarization. Public Opinion Quarterly, 76(3), 405-431.
Aliases	Political Social Identity Scale, Partisan Social Identity Measure, Expressive Partisanship Scale	Affective Polarization Index, Partisan Affect Gap, Thermometer Difference Measure
Related	4	4
Summary	Social identity measurement in political behavior applies social identity theory (Tajfel & Turner, 1979) to political groups, treating partisanship, ideology, or movement membership as a social identity rather than a mere instrumental affiliation. Huddy, Mason and Aaroe (2015) adapted Mael and Tetlock-style identity items into a partisan social-identity scale that measures expressive, emotionally charged group attachment and predicts campaign activity and political emotion better than issue agreement.	Affective polarization measurement quantifies the gap between how positively people feel toward their own political party (the in-party) and how negatively they feel toward the opposing party (the out-party). Iyengar, Sood and Lelkes (2012) showed that this affective divide has grown sharply even where issue positions have not, reframing polarization as a social-identity phenomenon of partisan like and dislike rather than ideological distance.