“…A considerable amount of research has proven consistent with behavioral momentum theory, which offers a useful conceptualization for understanding reinforcement history and current behavior, including persistence of drug use (Quick & Shahan, 2009), relative relapse of responding across rich and lean contexts (Podlesnik & Shahan, 2009), and resistance to disruption of discriminations by individuals with severe mental retardation (Dube & McIlvane, 2001). Greater resistance to disruption of behavior following higher rates of reinforcement has also been demonstrated across a number of species including rats, pigeons, and humans (Dube & McIlvane, 2001;Podlesnik & Shahan, 2009;Quick & Shahan, 2009), and occurs regardless of relative baseline response rates in the rich and lean components (e.g., Nevin, Tota, Torquato, & Shull, 1990;Podlesnik & Shahan, 2009), the qualitative nature of the reinforcer (e.g., food or milk; Grimes & Shull, 2001; drug or nondrug; Shahan & Burke, 2004), or the way in which reinforcers are delivered (e.g., rate or magnitude; Nevin, 1974).…”