Viki was taught to vocalize using the same reinforcement-based learning procedure used with Franz and Betty: she was rewarded for producing any sort of noise at all. Then another behaviorist trick came into play: shaping the response they wanted. Shaping normally refers to a series of successive approximations, but here they actually used their fingers on Viki’'s lips to assist in making the proper vocalization. This was followed by fading (only passively putting their fingers on Viki’s lips, then not even touching her at all). It was such a struggle that Viki put her own fingers on her lips to assist in the proper vocalization.