How effective are posters in altering people’s perceptions? Are theyonly worth the paper they’re printed on or are they truly persuasivepapers? The debate rages at the exhibition Signs of Change: Social Movement Cultures 1960s to Now at Exit Art inNew York, where hundreds of posters, photographs, moving images, audioclips, and ephemera document more than 40 years of activism, politicalprotest, and campaigns for social justice. Many of them have indeedaltered perception and triggered action. Curated by Dara Greenwald andJosh MacPhee and organized thematically, the current show presentsissues from Civil Rights and Black Power in the United States todemocracy in China to anti-apartheid in Africa to environmentalactivism and women’s rights internationally. “The exhibition alsoexplores the development of powerful counter-cultures that evolvebeyond traditional politics and create distinct aesthetics,lifestyles, and social organization,” say its organizers. Exit Art exhibitions are famous for presenting a critical mass of unique artifacts and this one is no exception.