Rachel Federman: In this clip from the 1970s, Riley explains the dynamics of repetition, rhythm, and pace in undulating works such as this one:
Bridget Riley: Repetition acts as a sort of amplifier for visual events, which seen singly, would hardly be visible. But to make these basic forms release the full visual energy within them, they have to breathe, as it were, to open and close, or to tighten up and then relax. A rhythm that's alive has to do with changing pace, and feeling how the visual speed can expand and contract; sometimes go slower, and sometimes go faster. The whole thing must live.