“…In terms of the feedback procedures discussed earlier, token-economy studies have included tangible, symbolic, verbal, and verbal-directional feedback information delivered in an endless variety of combinations, usually without controls for the relative effects of each (e.g., Staats & Butterfield, 1965;Staats, Minke, & Butts, 1970;Staats et al, 1964;Walker & Hops, 1976;Willis, Morris, & Crowder, 1972;Wolf, Giles, & Hall, 1968). In some research, tokens have not been delivered until the end of a remedial instruction period (e.g., Chadwick & Day, 1971;Knapezyk & Livingston, 1973;Walker & Hops, 1976).…”