The chief reason for testing reinforcement value in the laboratory setting is that measures yielded by such testing show a good correspondence to a product’s addiction potential in real-world use (Haney and Spealman, 2008). Specifically, drugs that have a positive subjective evaluation and are self-administered in laboratory tasks are ones that tend to be used and abused recreationally in real-world use (Comer et al., 2008; Haney, 2009).
The reinforcement value of an agent (e.g., a specific drug, such as nicotine) or a product (i.e., a drug[s] provided via a particular delivery system, such as smokeless tobacco or cigarettes) can be gauged through animal research; however, in the present situation, animal research on reinforcement value does not appear optimal. First, animal research is especially warranted when the product poses significant immediate health risks. However, to the extent that an MRTP has been adequately screened in preclinical work, it seems that the MRTP could be safely used in laboratory assessments of reinforcement value or self-administration (where toxic effects of possible prolonged dual use would not pertain). Second, because of the difficulty in modeling certain kinds of delivery systems with particular tobacco products (e.g., snus), human research may present the most externally valid research option. Third, human research methods afford an array of research paradigms that should yield meaningful assessment of MRTP reinforcement potential. Finally, human research requires less extrapolation because of a lack of interspecies differences, which can be substantial in terms of nicotine reinforcement (Rogers et al., 2009).
Key Considerations for Reinforcement and Self-Administration Studies
Almost by definition, an addictive agent must support self-administration. Moreover, there is a long history of research that shows a rough correspondence between the reinforcement capacity of an agent in the laboratory setting and its abuse potential in real-world contexts (Comer et al., 2008; Haney, 2009). Reinforcement is generally defined as the capacity of an agent to sustain self-administration. Therefore, one meaningful step in assessing the ability of an MRTP to support self-administration in real-world contexts is to determine whether it supports self-administration in laboratory or controlled settings.
Evaluating reinforcement is complicated by several factors, one of which is a continuum of reinforcement potency. Therefore, methods must capture the reinforcement potential of a product relative to other products or agents to provide meaningful comparisons. In theory, a desirable MRTP should be somewhat more reinforcing than nicotine replacement therapies (NRTs), but perhaps less reinforcing than conventional cigarettes (at least among current smokers who have demonstrated considerable