The repetitive peering down behavior of Brinp3−/− mice has been previously reported in the dopamine transporter (DAT knock-out) mouse model for ADHD as the “cliff avoidance reaction” (Yamashita et al., 2013), which could indicate that changes in synaptic dopamine levels may contribute to this behavior in Brinp3−/− mice. The gene discussed is SLC6A3; the disease is attention deficit-hyperactivity disorder.