“…On one hand, it has been found that humans perform Matching to Sample consistent with trainings in which conditional discriminations were not explicitly reinforced, either they were simple discriminations (Vaughan, 1988;Sidman, Wynne, McGuire & Barnes, 1989;Smeets, Barnes & Roche, 1997;Smeets, Barnes & Cullinan, 2000;Debert, Huziwara, Faggiani, Siomes de Mathis & McIlvane, 2009;Debert, Ma-tos & McIlvane, 2007) or respondent-type trainings (Leader, Barnes & Smeets, 1996Smeets, Leader & Barnes, 1997;Leader & Barnes-Holmes, 2001a, 2001bClayton & Hayes, 2004).…”