The DRD4 -521C allele has been associated with schizophrenia (Okuyama et al., 1999; Xing et al., 2003; Allen et al., 2008) and healthy individuals homozygous for the C allele showed a decreased ERN and decreased post-error slowing compared to T homozygotes (Kramer et al., 2007). Here, DRD4 is linked to schizophrenia.