Mean number of licks/stimulus trial (A), lick difference scores (B), latency to initiate licking (s) (C) and total number of trials sampled (D) for sucrose as a function of concentration in selectively bred P, NP and non-selected WI rats during brief-access testing. Lick difference score = mean licks to stimulus - mean licks to deionized water. Mean (±SEM) data are shown. Significant difference between *P vs NP, +P vs WI, #NP vs WI (P < 0.015).