Finely honed and diligently rehearsed performance is a hallmark of artistic professionalism, yet for some forms — comedy, acting, jazz — improvisation allows performers to expand boundaries, explore new ideas and integrate audience reaction into the live experience. Dance can be included in that list, with L.A. the home base for a clutch of choreographers and dancers considered leaders in the field of improvisational dance. For the third year running, organizers assembled a week of jam sessions and movement workshops with such luminaries as Carmela Herman, Christian Swenson, Stefan Fabry, Stephanie Nugent, Emile Hassan Dyer, Lionel Popkin, Jones Welsh, Hassan Christopher and Shel Wagner Rasch. Results of the exploration can be viewed at two performances that conclude the festival. Highways Performance Space, 1651 18th St., Santa Monica; Fri.-Sat., Jan. 5-6, 8:30 p.m.; $20, $15 students & seniors. (310) 315-1459 or www.highwaysperformance.org.