Singer and anti-gay activist Anita Bryant covers her face after being hit with a pie during a news conference in Des Moines, Iowa, in October 1977. In what would become one of their most infamous "zaps," activists sought to embarrass Bryant for leading a campaign against gay rights.
PHOTOGRAPH VIA BETTMANN / GETTY IMAGES

Charles Silverstein was a grad student in psychology when he attended a workshop at a behavioral therapy convention in October 1972. The topic was aversion therapy, a form of pseudoscientific conversion therapy in which gay men were administered electric shocks and other stimuli to “cure” their sexual attraction to other men.

But Silverstein wasn’t there to learn. He was there to shut the workshop down. As a leading psychologist took the podium, Silverstein hurried to the front of the room and introduced himself as a gay activist.

“We’re going to interrupt your presentation,” he told the speaker. “We’ll give you 10 minutes to speak, and then we’re taking over.” He made good on his promise, prompting chaos in the presentation room as angry protesters and participants began to debate the issue.

The speaker had just been “zapped.” Pioneered by gay liberation activists in the early 1970s, zapping combined protest with performance art.