How Yvonne Rainer's art shaped new ways of watching as well as performing; how it connected 1960s avant-garde art to politics and activism. In her dance and performances of the 1960s, Yvonne Rainer famously transformed the performing body--stripped it of special techniques and star status, traded its costumes and leotards for T-shirts and sneakers, asked it to haul mattresses or recite texts rather than leap or spin. Without discounting...