The Neo-Concretists were interested in how art could be used to "express complex human realities." They soon began making artworks the spectator could interact with physically, like Clark's Bichos (Critters), 1960–63, which are ingenious arrangements of hinged metal plates that can fold flat, or be unfolded into three dimensions and manipulated into many different configurations. Interacting with these works the spectator was meant to become more aware of his or her physical body and metaphysical existence. Viewer participation was essential for the artwork to be complete (in fact, Clark and Oiticica referred to the audience as "participants" rather than viewers. Clark described the exchange between viewer and "Bicho" as a dialogue between two living organisms. In addition, Neo-Concretists looked to push the limits of what art represented. For them, the art is the actual process of doing, and it is during this interaction that the spectator truly experiences what the artwork means.