Acid tests are events that emerged in the 1960s, primarily associated with the counterculture movement and the use of the psychedelic drug LSD. These gatherings often featured live music, art, and light shows, creating an immersive environment for participants. The term "acid test" originally referred to a method for determining the purity of gold, but it was repurposed to describe these experiences that tested the boundaries of consciousness. The most famous acid tests were organized by the Merry Pranksters, a group led by author Ken Kesey. They aimed to explore the effects of psychedelics on perception and community, promoting a sense of unity and expanded awareness among attendees. These events played a significant role in the popularization of psychedelics in American culture.