This paper presents findings from our empirical study of the creative process of improvisation, which has rarely been the subject of research in cognitive science. In this study, battle scenes in street dance were selected as an example of improvised performances. We conducted an experiment to investigate real-time cognitive processes. The results indicated three features: 1) Dancers mainly used well-practiced patterns, and discovered new patterns of dance; 2) In the process of discovering new patterns, dancers often utilized errors in their performance; 3) The processes of discovery were different in the performance of one dancer (solo scene) and the performance of two dancers (battle scene). In solo performance, dancers discovered new patterns by concentrating on their patterned dance. In battle performance, dancers discovered new patterns by utilizing stimuli from the situation (e.g. the music, their opponent) and using errors as an opportunity to loosen the constraints of their well-practiced patterns.