Both, the A-allele (Taq1A) and the G-allele (DARPP-32), have previously been considered risk alleles for various conditions and behaviors involving maladaptive cognitive flexibility, such as addiction (Smith et al., 2008; Munafò et al., 2007; Deng et al., 2015), schizophrenia (Meyer-Lindenberg et al., 2007; González-Castro et al., 2016; Albert et al., 2002), or impaired reinforcement learning (Frank et al., 2007; Doll et al., 2011). This evidence concerns the gene PPP1R1B and schizophrenia.