“…Such responses are popular because they are easy to instrument, and their use maintains continuity with animal studies in the area. Researchers also have recorded pulling plungers (e.g., Ayllon Bennett & Cherek, 1990;Katz, 1973), moving a computer mouse (Crosbie, 1990(Crosbie, , 1993, moving objects with a hand , stuttering (Flanagan, Goldiamond, & Azrin, 1958), muscle twitches (Hefferline & Keenan, 1961), heart rate (Brener, 1966), skin conductance (Grings & Carlin, 1966), and vocalization (Miller, 1968a,b). One of the hallmarks of human operant research is the creativity of experimenters in terms of responses employed.…”