4/ Take a social example: in these Serbian protests, multiple attitudes like “sex before marriage is OK,” “men can love men,” or “God should be obeyed” are compressible as a single dichotomy – RELIGIOUS or LIBERAL: if you knew someone’s answer to one, you could guess them all.

5/ We hypothesize that polarization exists when socially structured attributes align with group identities to create a compressible identity information space where knowing someone’s group identity allows you to guess related attributes. Conversely, knowing some attributes tells you their identity.