Compare methods

	Affective Polarization Measurement	Social Identity Political Measurement
Field	Political Psychology	Political Psychology
Family	Process / pipeline	Process / pipeline
Year of origin	2012	2015
Originator	Shanto Iyengar, Gaurav Sood & Yphtach Lelkes	Leonie Huddy, Lilliana Mason & Lene Aaroe
Type	Composite survey index	Self-report identity scale
Seminal source	Iyengar, S., Sood, G., & Lelkes, Y. (2012). Affect, not ideology: A social identity perspective on polarization. Public Opinion Quarterly, 76(3), 405-431.	Huddy, L., Mason, L., & Aaroe, L. (2015). Expressive partisanship: Campaign involvement, political emotion, and partisan identity. American Political Science Review, 109(1), 1-17.
Aliases	Affective Polarization Index, Partisan Affect Gap, Thermometer Difference Measure	Political Social Identity Scale, Partisan Social Identity Measure, Expressive Partisanship Scale
Related	4	4
Summary	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.	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.