CHRNA6 and Anxiety: To determine whether the humanized CHRNA6 3′-UTR SNP knock-in impacts baseline behaviors (e.g., food reward, locomotor activity, anxiety-like behavior, Figure 2A), we first evaluated mean responses during food self-administration at Fixed Ratio (FR)1 and then escalated to higher schedules of reinforcement at FR2, FR5, and Progressive Ratio (PR) (Figure 2B,C).