“…For example, only 4 to 11 sessions were required for participants to successfully learn the discrimination in four previous studies that investigated the discriminative-stimulus effects of dopaminergic psychostimulants (Hart, Haney, Foltin, & Fischman, 2002; Oliveto, Rosen, Woods, & Kosten, 1995; Rush, Stoops, Wagner, Hays, & Glaser, 2004; Stoops, Lile, Glaser, & Rush, 2005). In contrast, rats and nonhuman primates may require as many as 60 sessions to acquire the discrimination in preclinical drug-discrimination experiments (e.g., Czoty, Ramanathan, Mutschler, Makriyannis, & Bergman, 2004; Gatch, Taylor, Flores, Selvig, & Forster, 2006; Munzar, Baumann, Shoaib, & Goldberg, 1999; Powell & Holtzman, 2000). Despite the considerable investment required to train laboratory animals in drug-discrimination studies, an offsetting strength is that data collection with animals can continue for a considerably longer period of time relative to humans.…”